Somewhere (which I cannot find right now...), but if you look under the Ask Mike section, there is a great article he wrote where he addresses such an occasion.
The best thing to do before bringing your car in for service is to plaster "DO NOT WASH" signs on the windows, steering wheel and anywhere you can think. Make sure to tell the service adviser the same thing.
Luckily this trend has not hit NH yet, (I think...) as the local dealers I frequent do not wash the cars. However, I had a garage queen in a dealer body shop last summer for a minor thingy, and for some reason, even after seeing that the car was "competition ready" they seemed to think washing it was a great idea... Probably with brushes that they dipped in standing water on the ground to save money. Needless to say, in-between doing other clients cars, I took 4 days to get my car back in order. Thanks to Pinnacle Advanced Compound, a few spot buffs of Megs 105, Pinnacle Advanced Finishing Polish and a finishing touch of Pinnacle Black Label Diamond Coating v1.
It's a real PIA when someone thinks they're doing you a favor... when in reality they're causing you much heartache.