When my GTD got rear ended, both numberplate lights were pushed up and into the bumper a little, but not so much that you couldn't see it and that was a 20mph clout that dented and split the bumper. If someone has tickled your car with a 3mph kiss then I doubt yours have popped into the bumper.
Chances are someone has popped it out, uncoupled it from the wiring, pushed the wiring into the hole and made off with it. Shocking that VW didn't design these better in terms of security seeing as they go to the effort of protecting your wipers under the back of the bonnet.
Get a wire coathanger in there and find the loose end (carefully), then buy a new one and fit it yourself in seconds.