If there’s a legitimate issue with Roblox Studio saving to Studio you can rollback your game to the version it’s published on while Roblox Studio is closed and reopen the Studio after a couple minutes.
Honestly seems like you’re just opening a separate place then. Are you sure you’re not editing like maybe a local game you have saved to your computer instead of the published game (and the right published game if multiple)?
Odd. Maybe a plugin that’s removing everything when you get on studio? This is unlikely but still 100% possible. Have you gotten any new plugins recently before this issue started occuring?
Try looking in output, maybe it’s failing to load game assets. Or try republishing the game and opening that studio. Maybe, if you did make a local backup on your computer, open that and publish that as the game if the models are working fine.