SU2023, iMac. SketchUp works well for me and functions as it should. But when I open my SketchUp file in the morning I get a dialog box asking me if I want to open a more recent version of the file. I always save my file right before closing it so I am assuming the autosave is also saving a second later thus the “newer” version.
Probably the program crashed and it was autosaved before your last save, check if the newer version has all the elements you saved, if its an older version of the file just close that file open the one you saved and delete the autosaved version.