This is why one of my guilty pleasures is the World's Dumbest TV series down here in the States, hosted by a pack of celebrity has-beens and nobodies. Not sure if you get it up in Canada.
I used to own a snowmobile, was a little surprised to see that one take off on its own. The throttle is a spring-loaded thumb lever on the right handgrip, that always returns to idle if you aren't pressing it. I must assume the tumble somehow jammed the mechanism to wide open.