I flew DEN-IAH on CO this past Friday evening. I got to the airport a little earlier than anticipated, and the DEN-IAH flight before mine had not left yet. When I got to the gate, I put myself on the standby list for the earlier flight. Then I took another look, saw the gate area was packed and that since I would likely get a middle seat, I decided, no, I would rather take the later flight I had originally reserved, as I had an upgrade on it.

So I left the gate area and went up to the President's Club, where I got my boarding pass for the later flight. I did not tell the agent there that I had put myself on the standby list for the earlier flight. Then I had a couple of nice leisurely hours at the club.

When I boarded (10 minutes before takeoff), I was surprised to find someone else sitting in "my seat." We played "dueling boarding passes," and were surprised to find that we both had 1A. I told the FA what was going on, she checked back with the gate, and they sent me back to the gate agent, who said that there was no record of my reservation in the system.

When I explained that I had been on standby for the earlier flight, but opted not to take that flight, she told me that in such a situation, my reservation would be cancelled out of the computer. She also said the computer showed no record of my return flight; it had also been cancelled. She apologized that there were no longer any seats in first, gave me an empty row to myself in coach (not so bad), and told me that she would take care of the return reservation.

I did not get upset as I felt I had flubbed it (not CO) by not showing up for the earlier flight when I was called for my standby seat. I felt lucky to get a seat on the later flight.

(BTW, when I got to IAH, I checked my return res, and indeed, she had made the reservation and gotten me upgraded on it.)

My sense is that I messed up by not taking myself off of the standby list, but I would like to get a clarification. Given that I put myself on the standby list, and then got a boarding pass for the next flight, is it normal that I was been cancelled out of that later flight because I didn't show up for the flight I stood by on?

I think your assessment is correct. It is important to give each agent (lounge or gate) all the info. I am surprised that the lounge agent didn't catch the standby on your file though.

A little lesson, with no negative results. You had risked your flight and your return flight by forgetting the golden rule. Do unto others.... Your a lucky person. Wonder what you might have wrote on this board, if, you did not get on the next flight?