Hi
Turning the rotors is pretty standard on a good brake job. You didn't get great mileage out of your brakes at 15K, though.. Is this mostly city stop and go driving or something?
If the vibration was something that you noticed a while ago, think when the last time was when that tire was removed. It could be that whomever had your tire off last torqued your lugs nuts too much, causing eventual warping of the rotors (which causes vibration). If that tire removal was the same dealer, you can probably argue that point because 15K is too low for normal driving.
Years ago I had a dealer argue with me that the vibration I felt was ABS. The car was new and it didn't even have ABS - never mind that ABS doesn't work that way. Sometimes you have to argue with these guys.
Some rust on brakes is expected - they are made of steel. I could be wrong, but normal rust usually does not cause vibration, but warping does.
Others here probably also have some good ideas on this. Regards, Remco