I checked & nothing in Overrun deletes or renames saves. Every version since launch reads the same saved data, and no update clears it.
The cause is almost certainly the browser itself. On itch.io, progress is stored only in the player's browser, on that one device. It disappears when:
- The player is on iPhone/Mac Safari. Safari automatically erases saved data for games embedded on other sites if the player doesn't come back within about 7 days. This is the most likely cause.
- The player cleared their browsing data or used private/incognito mode.
- The player switched browser or device. The progress was never on the new one.