diff --git a/crates/ui-egui/src/panels/library_panel.rs b/crates/ui-egui/src/panels/library_panel.rs
index 6ef14648e..2c167e35a 100644
--- a/crates/ui-egui/src/panels/library_panel.rs
+++ b/crates/ui-egui/src/panels/library_panel.rs
@@ -244,9 +244,17 @@ fn missing_file(app: &VectorcraftApp, k: Kind, id: &str) -> Option<String> {
     (k.name)(app, id).is_none().then(|| s.path.clone().unwrap_or_else(|| id.to_string()))
 }
 
-/// The name of missing library `id` of `k` ([`missing_file`]): its file's name without the extension.
+/// The file of library `id` of `k` when its panel is open and the library can't be found,
+/// Persistent or not (a panel whose Persistent a command turned off stays open until [`tidy`]).
+fn open_missing_file(app: &VectorcraftApp, k: Kind, id: &str) -> Option<String> {
+    let s = settings(&app.ui, k.kind, id).filter(|_| is_open(&app.ui, &panel_id(k.kind, id)))?;
+    (k.name)(app, id).is_none().then(|| s.path.clone().unwrap_or_else(|| id.to_string()))
+}
+
+/// The name of missing library `id` of `k` ([`missing_file`], or [`open_missing_file`]): its file's
+/// name without the extension.
 fn missing_name(app: &VectorcraftApp, k: Kind, id: &str) -> Option<String> {
-    let file = missing_file(app, k, id)?;
+    let file = missing_file(app, k, id).or_else(|| open_missing_file(app, k, id))?;
     Some(std::path::Path::new(&file).file_stem().map_or_else(|| file.clone(), |s| s.to_string_lossy().into_owned()))
 }
 
@@ -393,9 +401,10 @@ pub(crate) fn library_name<'a>(id: &str, name: &'a str) -> &'a str {
 }
 
 /// The opener of library `K`'s libraries (`window.swatchLibrary {library}`): open library `library`
-/// (an id or a name, or the id of a missing library's persistent panel, [`missing_file`]) in its
-/// own panel, floating, or bring its panel forward when it is open; `null` closes every panel of
-/// `K`'s libraries. → {open, panel, name, count} (a missing library: its [`missing_name`], count 0)
+/// (an id or a name, or the id of a missing library's persistent or open panel, [`missing_name`])
+/// in its own panel, floating, or bring its panel forward when it is open; `null` closes every
+/// panel of `K`'s libraries. → {open, panel, name, count} (a missing library: its
+/// [`missing_name`], count 0)
 pub(crate) fn open_command<K: LibraryKind>(app: &mut VectorcraftApp, p: &Value) -> Result<Value, String> {
     let Some(key) = p.get("library").filter(|v| !v.is_null()) else {
         for panel in open_panels(&app.ui).into_iter().filter(|p| parse(p).is_some_and(|(k, _)| k.kind == K::KIND)) {
@@ -488,8 +497,8 @@ pub(crate) fn command(app: &mut VectorcraftApp, p: &Value) -> Result<Value, Stri
     }))
 }
 
-/// `ui.libraryPanel.locate {panel, path?}`: Locate Library… of a library panel whose library is
-/// missing ([`missing_file`]; any other panel is an error). Load the library at `path`, else one
+/// `ui.libraryPanel.locate {panel, path?}`: Locate Library… of a library panel whose library can't
+/// be found, Persistent or not (any other panel is an error). Load the library at `path`, else one
 /// picked in an open dialog (on the web the picked file arrives later and opens in a panel of its
 /// own, as Other Library…'s does), and show it in open panel `panel`, which keeps its view, Show
 /// Find Field and Persistent. When the file's library has a panel open already, `panel` closes and
@@ -501,7 +510,7 @@ pub(crate) fn locate(app: &mut VectorcraftApp, p: &Value) -> Result<Value, Strin
     if !is_open(&app.ui, given) {
         return Err(format!("library panel `{given}` isn't open"));
     }
-    if missing_file(app, k, id).is_none() {
+    if (k.name)(app, id).is_some() {
         return Err(format!("library panel `{given}` isn't missing its library"));
     }
     let path = p.get("path").and_then(Value::as_str).map(str::to_string);
@@ -1333,6 +1342,58 @@ mod tests {
         let _ = std::fs::remove_dir_all(dir);
     }
 
+    #[test]
+    fn locate_library_reads_a_missing_library_whose_panel_is_no_longer_persistent() {
+        let dir = std::env::temp_dir().join(format!("vc-locate-not-persistent-{}", std::process::id()));
+        let _ = std::fs::remove_dir_all(&dir);
+        std::fs::create_dir_all(dir.join("moved")).unwrap();
+        let palette = "GIMP Palette\nName: Brand\n#\n255   0   0\tRed\n";
+        let gpl = dir.join("Brand.gpl");
+        std::fs::write(&gpl, palette).unwrap();
+        let mut app = app();
+        let brand = panel_of(app.run("window.swatchLibrary.other", json!({"path": gpl.to_string_lossy()})).unwrap());
+        app.run("ui.libraryPanel", json!({"panel": brand, "persistent": true})).unwrap();
+        std::fs::remove_file(&gpl).unwrap();
+        let mut next = restarted(&app);
+        // After a command turns Persistent off, the panel stays open on its missing library until the next frame's tidy.
+        next.run("ui.libraryPanel", json!({"panel": brand, "persistent": false})).unwrap();
+        assert!(is_open(&next.ui, &brand));
+        let moved = dir.join("moved").join("Brand.gpl");
+        std::fs::write(&moved, palette).unwrap();
+        let r = next.run("ui.libraryPanel.locate", json!({"panel": brand, "path": moved.to_string_lossy()})).unwrap();
+        let located = panel_id("swatches", &format!("loaded/{}", moved.to_string_lossy()));
+        assert_eq!((r["panel"].as_str(), r["persistent"].as_bool()), (Some(located.as_str()), Some(false)));
+        assert!(!is_open(&next.ui, &brand) && is_open(&next.ui, &located), "{}", next.ui.status);
+        let (_, id) = parse(&located).unwrap();
+        assert!(SwatchLibraries::get(&next, id).is_some_and(|(_, lib)| lib.swatch("Red").is_some()));
+        tidy(&mut next);
+        assert!(is_open(&next.ui, &located), "its library is there now");
+        let _ = std::fs::remove_dir_all(dir);
+    }
+
+    #[test]
+    fn an_open_panel_whose_library_is_missing_is_brought_forward_by_its_id_when_not_persistent() {
+        let dir = std::env::temp_dir().join(format!("vc-open-not-persistent-{}", std::process::id()));
+        let _ = std::fs::remove_dir_all(&dir);
+        std::fs::create_dir_all(&dir).unwrap();
+        let gpl = dir.join("Brand.gpl");
+        std::fs::write(&gpl, "GIMP Palette\nName: Brand\n#\n255   0   0\tRed\n").unwrap();
+        let mut app = app();
+        let brand = panel_of(app.run("window.swatchLibrary.other", json!({"path": gpl.to_string_lossy()})).unwrap());
+        app.run("ui.libraryPanel", json!({"panel": brand, "persistent": true})).unwrap();
+        std::fs::remove_file(&gpl).unwrap();
+        let mut next = restarted(&app);
+        // After a command turns Persistent off, the panel stays open on its missing library until the next frame's tidy.
+        next.run("ui.libraryPanel", json!({"panel": brand, "persistent": false})).unwrap();
+        let (_, gone) = parse(&brand).unwrap();
+        let r = next.run("window.swatchLibrary", json!({"library": gone})).unwrap();
+        assert_eq!((r["panel"].as_str(), r["name"].as_str(), r["count"].as_u64()), (Some(brand.as_str()), Some("Brand"), Some(0)));
+        assert!(is_open(&next.ui, &brand));
+        tidy(&mut next);
+        assert!(!is_open(&next.ui, &brand), "a panel that isn't persistent still closes");
+        let _ = std::fs::remove_dir_all(dir);
+    }
+
     #[test]
     fn previous_and_next_show_the_neighbouring_library_in_the_same_panel() {
         let mut app = app();
diff --git a/docs/mcp.md b/docs/mcp.md
index 881253ac5..6fe656f45 100644
--- a/docs/mcp.md
+++ b/docs/mcp.md
@@ -1719,11 +1719,12 @@ under `ui.library_panels`.
 `ui.libraryPanel.locate {panel, path?}` is Locate Library…: it loads the library at `path` (without one, it
 asks for a file) as Other Library… does and shows it in the open panel `panel`, which keeps its view, find
 field and Persistent, and answers as `ui.libraryPanel` does. When the file's library already has a panel open,
-`panel` closes and is forgotten, and that panel is brought forward, made persistent when `panel` was. On a
-panel whose library isn't missing, it answers an error without asking for or loading a file, and the panel
-keeps its library.
+`panel` closes and is forgotten, and that panel is brought forward, made persistent when `panel` was. It
+runs on any open panel whose library is missing, with Persistent on or off. On a panel whose library isn't
+missing, it answers an error without asking for or loading a file, and the panel keeps its library.
 `window.swatchLibrary` and `window.graphicStyleLibrary` also take a missing library's id, so a closed missing
-panel opens again; they answer its file's name without the extension and `count: 0`.
+panel opens again, and an open panel whose library is missing is brought forward with Persistent on or off;
+they answer its file's name without the extension and `count: 0`.
 
 ```json
 {"name":"invoke_menu","arguments":{"command":"window.swatchLibrary","params":{"library":"pastels"}}}