I didn't know that Libby failed to qualify till after Pang was DQed. It was one of those races where I assumed Steffen and Trickett were a "gimme." She is the world record holder, you would figure at the very least she would pull a lane 7 or lane 2 assignemnt, instead she lost and ultimately she was overwhelmed.
This same circumstance happened to her in Athens as well. Then, minutes later it was announce that Pang was DQed.
From The Australian: Trickett swam a poor 54.10sec to finish fourth in her semi, a time which left her hopes of qualiying for the final hanging by a thread.
In the next semi-final minutes later, the first five swimmers to touch the wall under Trickett's time, leaving her ninth fastest and out of the final.
But then, in what Australian head coach Alan Thompson described as "some intervention from above"..." [Link]