More than gone from the gearbox....everything back there has fallen off, except for that bendy thingy that is still attached to the tail boom. The TRGB attaches to the tail boom independently of the vertical/horizontal fins, right? I might wildly imagine one or the other could fall off due improper maintenance, hard to imagine both would fall off.

Found the bits that fell off. Floating on the ocean not far from where the Robinson landed on the ocean. That has tail strike with ocean whilst in flight causing bits to fall off written all over it.

That doesn't look like tail parts floating. All that stuff would sink right to the bottom.

So far the best guess someone already posted above is a problem with the tail camera that this operation apparently used from time to time.

A wild guess says that a catastrophic TR failure occurred and the massive imbalance shook the gearbox and tail feathers from the boom.

From this amateur NTSB sleuth: I don't know anything about R-44's, but my guess would be that the last tail rotor drive shaft coupling (the one that attaches it to the gearbox) came undone. That left the shaft flopping around back there and it sawed the back end off. I've had *two* tail rotor failures in 206's. In both cases couplings came apart. Each time, the unsupported shaft sliced a big hole in what was below it - in this case of the 206, the tailboom. Seems to me that the R-44 t/r driveshaft runs inside the boom?

Yes, it runs inside and connects to the gearbox at the end via 4 bolts. In the R22 there is a little window through which you can look to check the torque stripes on said bolts. However, it has been a long time since I have flown a 44, and I've actually forgotten if it has that little window as well?