Could I please ask you to provide more details? How did you play the game (Browser? Download?), on what software (which browser? Which operating system?), did you do anything else? Was there anything specific in your run?
I've tried replicating that bug twice now. I've defeated and absolved the cat in our development environment as well as on Chrome, and neither of those times was my save file impacted.
I also invite you to the Discord (https://discord.gg/jHmzbJJr) if you want to chat about this there!