Do these three things first
- Reopen WPS — a Document Recovery pane usually appears with timestamps;
- If not, go to File → Backup and Recovery → Backup Management;
- Cloud documents can be rolled back from Version history.
Local cache
WPS keeps temporary files in a local cache folder; find its path under Settings → File Locations and sort by modified time for .bak files.
Prevention
Set auto-save to five minutes, keep important work in the cloud and enable "always keep a backup copy".