Found in my car parking spot.

I helped a friend put some furniture into his girlfriend’s car. Following morning, found this where he was parked the night before. Did we knock something off the car or is it a coincidence? It clearly slots onto something, is made of plastic… he reckons he looked at the car and couldn’t see anything missing but… I still think we might have knocked something from the interior when we put the seats down and hauled furniture into it, the spot I found it lined with where we had the rear passenger side door open.