While cleaning the Roadster I just purchased I noticed something and I have no idea how this could happen.

Below the Plate on the rear bumper ,right of center is the faint impression of a plate with marks for all 4 plate bolt holes. It almost looks like a die line molded into the bumper but I doubt that.
Its a perfect shape of a plate or plate frame. There is no metal that a dealer could have stuck a magnetic plate holder to. It way too deep to polish out as you can catch the edge with a finger nail.
Any ideas or thoughts ?

It looks like someone rear ended or the PO backed into another car and left the impression.
Is the paint and bumper flexible enough to do this without creasing or cracking ?

Thanks