I would guess that your car was used as a SRT Track Experience car, which would mean that a lot of people have driven your car pretty hard. The cars they use have a decal at the top center of the windshield. That's probably what you are seeing the remnants of. I would think they would be legally obligated to tell you that your car had been used in a race type event.

http://www.srttrackexperience.com/home.do