GTC58,
If the airplane was in heading select on autopilot it would have maintained this heading until flame out. If with wandering you imply the autopilot was off it would have crashed after a short while without any pilot intervention.
If it went into the FL400+ level and had an upset event and recovered, I would suggest that someone was flying it at that point.
My point is that later, after failed attempts to enter a route back to WMKK or deciding in a debilitated state to hand fly it, the crew became unconscious and the aircraft was uncommanded.
As a 777 pilot, you appear to disagree that in this condition, given fuel burn and CG changes in flight, the dynamic stability of the aircraft would be sufficient allow it to remain in the air. How long would it have lasted, do you think ?