Thanks everyone for your thoughts on this. I am now unafraid to call UA and ask about my "fare basis". I think I am going to draw the line trying to upgrade this flight: I would feel like a real jerk trying to upgrade a $50 transcon flight...on the other hand, it would make an even better story if I did.

A couple of other details on the whole experience so that others can learn should this situation ever occur again.

1) When the caution triangle came up on the screen after I pushed purchase, it said to call some 800 number "to verify the fare", which I did instantly. The agent on the phone was indignant when I asked her to please ticket my $50 flights and promptly canceled my reservation.

2) A friend (who makes fun of me for all of my time spent perusing FlyerTalk, nonetheless) called to say that he had also happened to be on ual.com and that his agent told him to hang on, they were going to examine each reservation before honoring all of them.

3) So I called the ual.com reservation number again and they said they would make a note in my file that I would like this reservation ticketed and that they would try to get it ticketed by the end of the day.

4) When it was not ticketed by the end of the day, I called again and asked the agent to do it while on the phone with me, which she did, cheerfully, I might add.

To me this situation suggests two things 1) if this ever happens again, book as many flights as possible and call all of your friends and 2) that they may have only ticketed the people that called in and nagged them, so this story has a familiar moral: "Keep calling back until they do what you want them to do"!