Parked our car at Uni. Went into a theatre, returned about 2 hrs later. Walking towards it I see someone trying to get into our car and being quite irate that the key didn't work. ( this was pre remote locking vehicles). They too had been at the same play and by now it was dark. So dark that their sheepish embarrassed looks were only just visible when they realised they'd parked their identical car (and similar number plate) 2 spaces further along.
This person probably would have noticed the lack of tow ball to put their bike back on (plus mine has kayak cradles).