I found this sitting in the driver's door cup holder of my 2020 RDX. It's made of foam and has 4 cuts in it so the piece can articulate. Pics show the top and bottom, and the white part is a little sticky. The quarter in the pics is for size reference.

Anybody know what this thing is?

 

It looks like one of many of the foam pads that are stuck all through the inside of cars to keep things from vibrating. Sometimes the guys on the line drop one.