I had something similar happen with playing Brotato on my Deck and PC, at some point there was a Steam Cloud error and my entire save got wiped. It’s frustrating since you can’t do anything. Steam Cloud is synced with your current saves and you can’t go back in time to change it unless you still have access to the files.

So if you have a pc that has the game installed I’d boot the pc up without starting Steam and see if your save games are still there and copy them some place safe. Then let steam sync and move back the savegames and launch the game.