Actually the RCMP do go up to the parking lots in question, where there is a vandalism/theft problem.
Solution? DON'T LEAVE ANYTHING IN YOUR CAR!!
It sucks, but stories like scott johnson's from Garabaldi Park do happen here. The best I can say is it probably had nothing to do with the WA plates on your car.
As for the story in the initial post? I don't know anything of this. I would be suprised if it had happened, and there was no stories of it floating around town by now. How about some more details, Jarred? Especially what campground it happened in?
40-50 people is a pretty big gang. Are you sure of that number? And a friend's sister in-law's, brother in-law... Has all the makings of an urban legend.
Could it be dru tired of the crowds at Squamish, trying to scare some traffic away?