One step closer to solving this
This is a test map after bombardment. Note even though this is a lot of rubble the buildings still show
This is a test map after I placed rough on every multi hex building registration hex
It would appear if rough is created in the registration hex of a building (any building ) during a bombardment the building will disappear but re-appear after the save is restarted because the process of saving and restarting removes the temporary rough hex that was created
That's the working theory ATM