I know the location of the captains body being found away from the FO's makes it speculation that he probably wasn't in the cockpit. A previous post stated that and it may or not be true. If the flight is more than 8 hrs each crew member is required to be off duty to make the flight legal. Usually it is divided up evenly so everybody gets a couple hours rest. Look at the recent Air India incident when the captain went back to pee and the FO pushed on the control column adjusting his seat and went into a high speed dive because he was inexperienced and in that case incompetent. Sometimes you have to use what you have left to keep control. I'm not saying holding attitude and gps ground speed would have worked but it probably was all they had. Hopefully they will recover the black boxes but doubt it will happen.