It's basically the same on the other side. The two sides are slightly coped a little different to make it easier to open maybe? I thought maybe it was supposed to be an insert for the map pouch on the back of the seat. Fits in width but sticks out too much to be for that. Was wondering if anyone else found such a thing in their car. I agree that it looked like something for the seat. But not really sure how it would have dislodged so easily.What's on the other side? Maybe it came from the seat bottom and fell down to the car floor.