itch.io

Have you been running the game via the itch app in "sandbox mode"? Itch then puts all files in a different folder and you can lose your progress.

When you normally run the game, your savegame will be saved here: 

C:\Users\<USERNAME>\AppData\LocalLow\Tiny Secret Games\Snapshot!

If you use the itch sandbox mode, it can be moved to a folder like:

C:\Users\itch-player\AppData\LocalLow\Tiny Secret Games\Snapshot!

Check that folder and copy the savegame over. If the app ever resets or recreates that sandboxed profile, those sandbox saves can also seem to vanish.