Limitations
Recovery in Poly is intentionally conservative: when restoring something would create an impossible state or resurrect something you explicitly destroyed, it's skipped rather than forced. Three cases to know about.
Folders that became ancestors
Folders can move, so history can contain arrangements that are impossible to recreate. If a folder you're rolling back to was inside some folder then, but is now that folder's parent (or a more distant ancestor), restoring the old arrangement would make the folder its own descendant — a cycle.
During a folder rollback, any entry that would recreate such a cycle is skipped along with its subtree, and the skip is reported in the rollback's summary. Everything else in the rollback proceeds normally. If you need that subtree's old contents anyway, restore the files inside it individually, or use Copy file at revision from Flashback.
Permanently deleted files
Deleting a file in Poly archives it, and archived files are fully recoverable — a folder rollback brings archived files back automatically, and rollbacks themselves archive rather than delete.
Permanent deletion — explicitly deleting a file from the Archive — is the one genuinely destructive act in Poly, and it is honored: permanently deleted files are not restored or reverted, and folder rollbacks skip them (with their subtrees) rather than resurrect them. This is deliberate; it's also why agents and integrations are blocked from permanent deletion entirely, and why the CLI makes you confirm it.
Files that never synced
Restore and revert operate on server-recorded history. A file whose upload the server rejected — most commonly for being over quota — was never accepted into that history, so there's nothing server-side to restore it from.
Such files aren't lost: they remain on the device that created them, in an offline-only state — still listed, still openable, clearly marked as failed. From there you can retry the upload (after fixing the cause) or remove the local copy. Until one of those happens, the file exists on that device only: it won't appear on your other devices, and it won't participate in version recovery. Note that the desktop app never evicts an unsynced file's local content, so the only copy is safe while you decide.