THE HELICOPTER DISAPPEARED WHILE ON AN OVERWATER FLT FROM KEY WEST, FL TO FT PEIRCE, FL. ONE OCCUPANT & THE WRECKAGE OF THE HELICOPTER WERE SUBSEQUENTLY RECOVERED FROM THE GULF OF MEXICO. THE PLT & THE OTHER OCCUPANT WERE NOT LOCATED & WERE PRESUMED DEAD. PRIOR TO DEPARTURE, 1 OF THE CREWMEMBERS WAS OVERHEARD TO SAY 'THAT DIDN'T SOUND GOOD'REFERRING TO SOME UNUSUAL SOUND AT THE TIME OF SHUT-DOWN. THE PLT TOLD A WITNESS THEY WERE HAVING MECHANICAL DIFFICULTY WHICH THEY WOULD CORRECT IN FT PIERCE. ANOTHER WITNESS HEARD THE PLT STATE TO 1 OF THE PAX THAT A CAP OR PART HAD FALLEN OFF & WAS MISSING. AN EXAM OF THE ROTATING & STATIONARY SWASHPLATES WHICH MADE UP THE STAR ASS'Y REVEALED THAT THEY HAD SEPARATED FROM EACH OTHER. A METALLURGICAL EXAM REVEALED THAT 8 OF THE 12 BOLTS WHICH SECURED THE ROTATING STAR INNER RACE TO THE ASS'Y HAD FAILED IN FATIGUE; THE OTHER 4 BOLTS WERE MISSING. THERE WAS EXTENSIVE DAMAGE TO THE BELLY, TAIL CONE & PYLON.