2016 Q3 Quattro Premium Plus Rear Brake Parts Question
 

Three weeks ago an auto service center that rhymes with Ears took my back brakes all apart to replace pads and rotors. They only realized after the car was disassembled that they had the wrong parts. So they put it back together and I picked it up.

Today, I hit a bump after highway driving for 3 hours and heard a rattle in the rear. The driver's rear caliper assembly pivots whereas the passenger's rear caliper assembly does not pivot.

Upon closer inspection, it appears that one of the bolts wasn't replaced by said auto service center or it was replaced and worked itself out within the last three weeks.

I'm attaching a picture of the part with the absent bolt. I see no such piece on parts.audiusa.com
I bought my card July 2015 and it is a model year 2016. I looked at the brake diagram for 2015 and see this piece there with a beautifully grayed out section 'parts no longer available'.

Anyone know anything about this?
Thanks
Sam
https://cimg9.ibsrv.net/gimg/www.aud...45a5d580ff.jpg