To a large extent, I think this thread is useless because we are never going to find out the facts. If I had been in the letter writer's shoes, I would have acted very differently and probably made it to PDX before he did. But that's because I've learned a few things that are admittedly not obvious a priori. In particular:

1. Never attempt to ticket a reservation at SFO. I don't care if you are a UGS trying to buy a $7000 one-way domestic full-fare F ticket. United simply will not do business with you in any reasonable amount of time. There is only one line in T3 and one in TG where they can issue tickets, and they simply won't prioritize you based on status or spending. Most of the people in this line are having some sort of problem, too, so even if there are only 3-4 people ahead of you, you can easily spend the better part of an hour waiting.
2. If you've missed a flight, never argue with the check-in agent. Just do whatever it takes to get yourself through security (e.g., standby for a later flight, or buy a refundable Y ticket), then rush to your original gate and ask the Gate agent to place you on standby for your original flight. If you are actually there at the gate, there is no reason for them not to let you on the plane. Outside of security, though, they won't give you the boarding pass.
3. If you truly have an emergency, don't call United. Call your credit card company. They can look at multiple airlines and figure out how to get you somewhere as fast as possible. That may not be on UA metal, but some things are more important than EQMs! (I know it's easy to forget this.)