It's here on the Southwest site:

http://www.southwest.com/hotfares/choice_offer.html

Maybe Choice got squeamish about drawing attention to a promotion with Southwest following the accident. In late summer 2001, Choice was heavily advertising a triple miles promotion that was to start Sept. 15; then they pulled it saying it wasn't a good time to promote air travel, but people could send their receipts in and get the triple miles.