I believe this is the coaster in question...
http://rcdb.com/id4132.htm
I wonder how much wind there was to completely stop it like that. Anyone have a clue other than a lot?
I have a feeling it may have more to do with the cold temperatures than the wind. Cold temperatures means tighter wheel bearings. That makes the coaster run a bit slower, and more importantly, makes it a bit harder to start rolling if it should stop. It may have been a freak gust that caused a slower than normal train to stop, and the fact that it was cold kept it there. My hunch is under "normal" circumstances this might have simply "rolled back" and not trapped the riders upside down.