I think I might have an idea of what went wrong. The level editor actually reads and writes to your saved progress (for spoiler-y reasons,) so it’s likely that something went wrong during that process.
Fortunately, this is the only report I’ve gotten in the three weeks since the game’s release, so hopefully this is a really rare bug.
I’ll try to implement some sort of save backup system soon, but in the meantime: what did your save game look like? I can try to recreate your progress, then give you a save file which you can load into the game via the JavaScript console.