fix(atomic): the vanished-backup error names the path it looked at

crates/format/src/atomic.rs

@@ -511,9 +511,10 @@ pub(crate) fn unresolved_recovery_error(dest: &Path, completion: &io::Error, res
     let msg = if restoration.kind() == io::ErrorKind::NotFound {
         format!(
             "cannot save {}: the previous version moved to its backup name but {RECOVERY_UNRESOLVED} from it \
-             (completing the save failed: {completion}; the backup no longer exists: {restoration}), \
-             so the destination currently holds no file under that name",
-            dest.display()
+             (completing the save failed: {completion}; the backup {} no longer exists: {restoration}), \
+             so the destination currently holds no file under that name — check whether it was moved",
+            dest.display(),
+            recovery.display()
         )
     } else {
         format!(

crates/format/src/atomic/meta/tests.rs

@@ -384,7 +384,8 @@ fn a_vanished_backup_is_reported_as_gone_rather_than_as_a_recovery_copy() {
         Path::new("/docs/.report.psd.9.pcsave.tmp"),
     );
     let msg = e.to_string();
-    assert!(msg.contains("no longer exists") && msg.contains("no file under that name"), "{msg}");
+    assert!(msg.contains(".report.psd.9.pcsave.tmp") && msg.contains("no longer exists"), "the vanished backup is named: {msg}");
+    assert!(msg.contains("no file under that name"), "{msg}");
     assert!(!msg.contains("survives at"), "no recovery promise for a vanished backup: {msg}");
     assert!(!msg.contains("the original file was not changed"), "{msg}");
 }