Isolated
When the time comes to leave, it is time to leave. Even if it means that I have to spend the next four hours hiding out in the restroom. Please consider allowing others to use the restroom while you are there. Is it possible that he simply did not realize that he was in a position where he could nod off while seated?
Even taking into account the fact that he did not consume any alcohol or sleeping aids in order to make it through the flight, it is likely that he did. Therefore, what is the most important takeaway here? I was so tired during the flight that I fell asleep in the restroom where everyone else was.