In your case I can see where an unexpected throttle opening could happen, stuff does happen. Someone at some point might have thought to crank the steering both ways and check throttle freeplay and throttle return when pressed, before returning the sled to the owner. (I do this regularly when working on anything that might remotely affect the throttle cable or throttle body). I check the throttle returns properly on my sled on Every ride, EVERY TIME. Stuff happens.
Off trail sleds get a lot more snow into the engine bay, which often causes the throttle to stick momentarily. We had one with a 600 Backcountry last year that they rode deep snow all day, parked the sleds, then started it the next day. The BS story was, the girl was sitting on the machine, started the sled, it idled for several seconds, then took off WOT across the lake and stopped at the treeline, bending a couple of A-arms. Total crap, because it can't open by itself, and if it was started with the throttle frozen open, an e-tec will only idle, until the throttle returns to zero then is re-applied. Being that it's a mechanically operated throttle body, and not a Throttle-by-wire, we knew it was total crap. Should have seen the mountains of ice everywhere in that sled, including the airbox .... I took pics to cover our asses if they came at us with a law suit.