Cannot find a leaking propane issue anywhere and am uncomfortable not being able to explain the massive discharge that was encountered.
Reading your post I can't see why system was venting either. If there was no impact or heat to your propane system can't see why it was venting.
Most RV's have a blow off valve. Here is a good example of a "pressure blow-off valve" doing what it should be doing around the 2 min mark. Sort of sounds like a whale or dauphin coming up for air.
Notice how it expels to atmosphere, watch for flames underneath.
I remember this vid because we take that road sometimes. Brings up couple good points IMO
1 You never know when something like this will happen. Prevention is best.
2 Your insurance limits can run out quick depending on something like this happens at.
And I have no idea where my blow off valve is actually at or if it even works and would like to find out. Just not the way the RV did in vid.
http://www.youtube.com/watch?v=3zSjZVlnKHg