It sounds to me like poor connections in the fault path, in which case the breaker may have been fine. The path could have provided enough resistance to not "pop" the breaker right away, also resulting in heat and spaterings of metal at each loose connection throughout the circuit.
As to the proper notification procedure: It would be a noble thing for you to report if indeed it was a manufacturer defect. Nothing in it for you, but the manufacturer could learn and/or take corrective action, curbing their liability and, more importantly, increasing future public saftey. All this of course if it was a bad breaker, otherwise a waste of time.
But if you did find out the quickest, easiest way to hande reporting such suspicions, either to UL or manufacturer, let us know. It'd be more likely to report such things myself if I didn't have to do the pre-research.
