Save files switched between user accounts, can't unswitch

My partner and I both had our Steam accounts on the Steam Deck handheld. After logging in one day I noticed that my account was loading a save file that was not mine (story mode not complete). We checked his account and my save file (with story mode completed) had somehow loaded onto his steam account. When logging into the computer the same error was still present. My partner decided he was willing to sacrifice his game to troubleshoot, but nothing we have tried has worked (trying to load with wifi/cloud disabled, copying program files, etc.)

So my save file is connected with his Steam account and there is a blank save on my account at this time. How can we restore my game data to my Steam account? Is there some way we can recover the cloud data or save it locally? We are nervous to play more on the save file in case it gets messed so haven't been able to play.

Thanks for any advice!!