Could someone please tell me (FLIFO) what happened to AA2312 DFW-ORD yesterday?

DFW was too much fun yesterday. I was originally on AA2323 and an agent at the admirals club put me on standby for the above flight, which experienced a magnitude of my favorite aa rolling delays. There was no plane at the gate until 4:00PM. If I would have stayed on my original flight, I just could have relaxed the whole time, and my upgrade would have cleared. To top it all off when I got to Chicago, I was told that I was rebooked on a UA flight. I went to the gate and boarded my original flight with no questions asked. IRROPS and aa are two things that don't mix.