I have a 2011 A4 6MT w/ 60k, and today I started to drive out of my parking spot and there was a loud clicking from under the back seats (or so) that got more rapid as I sped up. I was limping it to a local shop when the noise stopped and I noticed a small piece of plastic come out from under the car. There was has since been a low rumble type vibration coming from under the back seats or trunk.

Ideas?