If for any reason you restored from a backup and do not see your files, do NOT delete the app. You can still export the files inside the app, even if you do not see them showing in the app, by going to settings (top-right corner of Locker app) > Export All Files. Or you can export them using a tool like iMazing. Once you have them saved in another app (such as your Files app), you can re-share them into Locker.