"How can one fly a rotory aircraft without collective? Is it something about Bell Aircraft?"
I guess the answer could be yes; the safety design of the 412 (having the throttles on the collective) probably made the difference here.
You might have heard that the same (loss of collective control) happened to a 206L-4 a few days later in the GOM; in that case a control bolt fell out. Same outcome as the 412, all aboard unharmed.
