Emergencies on the way to your next duty station; how should it be handled?

The full range of responses could be used, depending on the commander. Best, if he was on leave or pass, would be to have it extended because of an emergency situation. He takes a few more days of leave, no harm, no foul.

I've seen Seniors just go "Get here when you can". I've also seen them called AWOL, even knowing exactly where they are and their situation. But the first solution is the most common and professional of the options.

I had a natural disaster emergency while I was trying to return from leave to my first post after Basic. A blizzard whited-out the airport and closed the interstate for days. I was three hours (by interstate) from the airport at the time. I called the Red Cross to utilize their liaison service which was fine, though it didn't do much for the bus breaking down as it was bringing us from the airport to post a few days later. I think the bus driver in that case called the CQ and it was passed on up. Not quite the same scenario as what you describe, but I think much of the treatment would depend on your relationship (or lack thereof) with your chain of command. Not ideal, obviously, but sadly the way most of such things go in my experience. I've been told to always call the Red Cross, no matter what. As a current Red Cross instructor, and having seen the changes going on the last few years, I would be far more hesitant now to place all my faith in that system, but it couldn't hurt if that's still the going piece of wisdom.

I hope he did call in, that would seem to be the sensible and logical thing to do.