This method may possibly/partially restore a save game that is corrupted by not exiting the client correctly.
- Go to C:\Users\[username]\AppData\Roaming\7DaysToDie\Saves\Random Gen\[seed]\Player
- Remove [number].ttp
- Rename [number].ttp.bak to [number].ttp
Player profile backup restored. Your items and everything you've built is still gone, AFAIK that's not backed up. But it's still better than having to start over entirely.