Recently, while backing up in my 04 Subaru Outback, I was certain I had hit something - a loud noise and sensation of hitting something was felt by both myself and a passenger. When I got out to look, there was NOTHING to be hit nor any damaage to the rear bumper. The service mgr. at the dealership has no clue and assures me calling the Subaru headquarters will not turn up any ideas on the cause of this…has anyone out there got any ideas???
Maybe you discovered, and promptly annihilated, evidence of extra-terrestrial life?
Actually, look in your trunk, and see if maybe something was or could be rolling around. Something relatively small, like a jug of oil or coolant, can cause a thump if it falls over, or hits one of the sides of the trunk.