Source control could be helpful here, as you mentioned! Retool should be doing a lot of page saves when you're working on apps, so losing app work shouldn't happen often (unless more than one person is trying to edit the same app).
That said, if you lose work, you can revert your app to a previous state. Just keep this warning in mind: If you make any changes to the canvas when traveling back in time, that past version will become your present version and it messes with the history, so be careful not to touch anything until you find the version you're looking for