so my save file just yeeted itself. anyone else too ?
This game is in fact just a particular type of web page, ran by your browser. That means that all the data the games saves is stored at the only place your browser is allowed to save anything, unless you explicitly ask it to download something: cookies.
Therefore if you deleted your cookies recently, your save files were deleted along with them. And even if you didn't, it's perfectly possible your browser decided this specific cookie was too old and deleted it itself, because cookies are by nature absolutely not meant to last forever.
If you want to preserve your save file over a long period of time, use the "Save to disk"/"Save to file" button at the bottom.