Update from ORD: I got to the LAS gate at SFO (big
to T1) 30 minutes before departure, and at T-20 they posted a 1 hour delay due to late inbound crew. (They were coming from ORD -- you'd think they could have figured it out a little sooner.) I was going to misconnect, but as
SunLover suggested, I saw an opportunity.
I talked to a gate agent and tried to explain my situation (misconnect in LAS on separate PNRs) and requested to be put on a nonstop SFO-IAD. The agent seemed willing, but both redeyes were F1 Y0 so she couldn't confirm me. She claimed to put me on the standby list and told me to go to the T3 ticketing desk where they could help me.
While taking the shuttle to T3, I got on the 1K line to explore other options. I had done some ExpertFlyer research, but every redeye from SFO to anywhere was sold out, so they couldn't help me. I got the phone agent to refund my SFO-LAS award ticket and cancel out the LAS-IAD flight, so the system wouldn't cancel my itinerary for missing that flight. At this point my plan was to try for standby on both SFO-IAD redeyes, and if both fail call a trip-in-vain and go home.
At the IAD gate the screen showed 5 pax on standby, none of which were me. The gate agent looked up my record, seemed confused, typed a while, printed out a BP-like slip which he kept, and told me he'd call me if a seat opened up. Apparently I was waitlisted for the flight, which is somehow different from standby -- neither the gate agent nor the 1K desk were able to explain the distinction to me.
Boarding starts and I stand near the podium to see what happens. There is one F seat open, and they upgrade SEA/S to 1A. Since Y is exactly at capacity, this should leave one seat -- except I now learn that seat 30A is broken, so the Y cabin is full.
More waiting. 10 minutes to go and one pax to board: it's SEA/S in 1A. The gate agent remarks, "He's a 1K, you'd think he'd know what he's doing." I smile. They page him on the plane, and when he doesn't answer they offload him, upgrade the next pax on the list, and hand me a BP for 21B.
(I don't know what happened to the other 5 on the standby list -- I'm guessing they were employees who found other flights.)
So in the end I was able to get the routing I wanted, refund my positioning flight, and get rebooked in full Y on a transcon. Not a bad haul!
Oh, and Mr. SEA/S: whatever shenanigans you were pulling, thank you.
A final note: I felt safe with a 40-minute turn in JAX because (a) it was on one itinerary, and (b) I had looked at UA's schedule in JAX and concluded that the inbound and outbound were extremely likely to be the same aircraft; this was in fact the case.