Hate to hear that... unfortunately, it sounds like the progress on your local machine may have gotten overwritten with an earlier, Steam cloud save.
Steam games sync their progress to the cloud every so often. Sometimes (very rarely!) overwriting happens if you've been kicked out of the game or off Steam, or have been playing offline and make progress, and then connect back up to Steam.
However, you CAN take preventative measures to make sure this never happens again. Use these steps every time you've been playing offline, then connect back up to Steam!
In fact, try these steps now, and see if your progress comes back!
- Launch the game
- Review the game to determine whether you are missing levels. This is a sign that the game is calling to a Steam cloud save with lost progress!
- If you're missing anything, shut down the game IMMEDIATELY!!
** DO NOT enter into gameplay and finish a stage at this point, or your local data save will be overwritten to reflect the progress you see on the character select screen. When the data re-syncs, you will find your missing progress has been lost permanently. **
- Close the Steam client to force a re-sync between the local save on your PC and your Steam cloud save.
We're gamers too, and we know how frustrating lost progress can be. We hope these steps will help you!