Unfortunately, I have some bad news. It looks like your save file may have gotten corrupted (which sometimes happens if the game or computer is force-quit during a save operation), or overwritten by a Steam cloud save. Here is a bit more information about this:
Is there any chance you have used Ctrl-Alt-Del to shut down your game, or right clicked on the game in your system tray and selected "Close Window"?
We definitely recommend you keep a backup of all your save files, just in case!
Dang man, I think I did one time when the game sorta froze on me. So is there nothing I can do? Thanks for the help
Aw... huge bummer. Yeah, definitely use that combo with extreme caution! It can interrupt save progress and corrupt data (for both games and other apps on your computer!).
You can try the recovery method from the article IF you have Steam cloud enabled, but unfortunately it doesn't always work.
1. Launch the game
2. Review the character select screen to determine whether you are missing levels, characters or money. This is a sign that the game is calling to a Steam cloud save with lost progress!
3. 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. **
4. Close the Steam client to force a re-sync between the local save on your PC and your Steam cloud save.
It looks like there's no recovering my save, but thanks for taking the time to help! Hopefully I'll have the time to do insane mode again and then I'll feel super accomplished for beating it twice!