You can get your save back using two methods if this happens to you.
Here are 2 methods that you can try.
When your save game shows as corrupt it might not actually be. In some cases only the timestamp got corrupt. This means your first attempt should be to just try and load the game!
Ok, the local save won't load you... You still have a cloud backup if you've been playing online!
The Perfect Tower II saves your progress into our cloud in addition to the local save and the steam cloud. This means that when you open the game and it shows a corrupt save game you will still have the option to load your save game from the cloud!
If the cloud says "offline" that means the game couldn't log you in. The game tries to log you in via Steam when you launch the game, but since we had a lot of server load it can happen that the log in won't work and you'll most likely have to restart your game to try again.