In my mk5 Golf days, before I was into car detailing, my car would almost always look dirtier after the dealer’s complementary service wash than it did before it was ‘washed’; sections missed, dirty muddy water streaks and dried on water spots. I ended up washing it myself when I got home from the dealers to remove evidence of their half-hearted attempt.
Needless to say, now I’m a car detailing fan, my car is never ever washed by the dealer. Weather permitting, it’s always washed before it goes back to the dealer for servicing, warranty work or repairs, with the ‘reminders’ to the dealer to ‘leave it alone!’ (do not wash’ hanger on the mirror, same instruction on a tag tied to the keys and do ‘do not wash’ instruction written on the service job card).
The irritating thing is I did the same and washed the car before on this occasion so they didn't drag grit across my paintwork. However the dealer didn't inform me they were washing the car until after the deed was done. 
That’s really annoying. Worth considering using the ‘reminders’ that I do, to minimise the risk of them doing it again in figure.
