That sounds about right! The game save is a cookie, so clearing your cookies will delete the save. It's safest to download it and play on that version instead.
I Didn’t know saves could be cookies.
I'm relatively inexperienced with HTML game development, but as far as I know, saves can only be cookies.
Nowadays most games are using LocalStorage, although that tends to be cleared at the same time as cookies
Somebody used clear all browsing data, including cookies for some reason *hides lotion*