Wow. I can't tell from the pics but did the red QD male end come out of the female socket or did the QD stay together and then the upper red covering and hose melt off? I see no way in hell the QD came apart by itself if it was locked together.
I have had the OEM one break off (the right angle one) while picking the tank up, and there was fuel everywhere, and very quickly. It could be the red one on yours was loosened somehow (tampered as you say?), that would start a misfire for sure, and then everything melts and looks disconnected.
Glad you are OK that sure must have been scary.