Do we have all hubcaps?

"I need to ship a box. Can we stop by the post office on our way to the soccer game?", I said.  Allison said yes.  On our way to the post office, as she was turning on to Walnut Street, she heard something behind the car.  She said she may have lost a hubcap and stopped the car for us to check the wheels.  All hubcaps were on.  So we kept going to the post office.  When we got there I asked "where's the box?" , and that's when I realized I had put the box on the car (not IN the car) while getting my soccer bag in the back seat and I left the box on the car.  The sound we heard was the box falling onto the middle of the street.  The next day I had this voicemail on my work line: