Sketchup models frequently save, but there is no option to revert to the last saved version.
I was working on a SketchUp model when it became corrupted (objects hidden behind walls became visible as dashed items). I lost a good deal of work. It would have been great if I could revert to the last saved version.
I just realized there is no Feature Request category for SketchUp Free so maybe it wouldn’t make much sense to move this. however, next time you can write in your post what version you refer to.