I've seen this happen to a nearly new bicycle and I think it's probably what happened to you. "Chain suck" happens when the chain climbs up the backside of the chain ring due to a tight link in the chain. If the tight link does not flatten out and when it reaches the rear derailleur it cannot travel through because it catches on a tab that the chain normally passes under. The load that you've put on the chain can rip the derailleur right off the bike. This is not normally covered by the warranty unless you can prove that the tight link was caused by the manufacturer or dealer. Tight links are very common and are often due to a lack of chain maintenance or poor installation technique. The tight link is often the link the chain was joined on.
In the case that I mentioned the dropout plate was ripped out of the frame. This required sending the frame back to the factory for repair.