if you had a nismo you wouldn't have had to worry because all the extra downforce on the car is designed to hold keyfobs in place on the windshield. The detailer must have mistaken your crappy non nismo 370z for the much better, aerodynamically superior nismo 370z.
that reminds me of a story when i was a little kid. i was playing basket ball in the driveway with my brother, i took my watch off and put it on the trunk of my mom's car and forgot about it. then later she went out and i realized i left my watch on her car. i ran down the block and found it in the middle of the road run over by a car.