Sounds odd - and I have no idea what a "vacume plate" or "vacuum plate" is in the rear assembly since nothing back there is vacuum controlled. The e-brake is mechanical and the regular brakes are hydraulic. I do, however, know 2 things:
1) It is VERY unlikely that the e-brake pad would have "fallen off" since it is not an item that would have needed replacement at any point, and not even something that would have ever been touched (ie: assembled incorrectly) since you have most likely never had your rotors off at only 22K
2) The only "plate" back there is the backing plate. This is listed at around 3.5 hours of time + brake bleeding (prob another hour) The labor for wheel bearing replacement should be included in that since it is required to remove in order to replace the plate. This is a $100 part. The plate I have no idea on, but figure it can;t be more than around $100 either.
3) A wheel bearing is NOT very difficult to replace, just tedious. Any indy shop should be able to handle this for you at a significant savings.
I would ask for a breakdown of parts and labor from the dealership for their $1200 quote. Just tell them that it seems kind of high and you were looking for some justification. Just out of curiousity, what were the symptoms you were having?