[What's_nitro?]

^ Exactly. Seeing as it was soo puffed up already when he saw it, if he had kept in inside it wouldn't have caught on fire. If it was going to spontaneously combust it would have done so long before he went to it. I seriously doubt it was sheer coincidental luck in timing that it only caught AFTER he threw it outside. It probably became damaged when it landed. And yes, the fireworks are fun and you would have missed them!!!