How could this have happened to my high school photo?

A few years ago I had, for some unknown reason, put my high school picture from a photo booth on the car dashboard. It’s very small about 2“x2”. I had my older daughter in the car with me. The next day it was missing. I looked on the floor of the car and in the glovebox. Behind and to the side of the car was a large trash barrel.
It was filled to the top with trash so I guess I had just moved into that house. I took the lid off the trashcan and was rifling down a couple layers—and there was my photo. Can anyone explain how it got into the trash barrel and how I found it in there? It wasn’t even on top.