On my last fight back from Kansas City to Houston May 4, I was advised that I was second on the stand-by list for the upgrade, but on the plane they upgraded an elite and later came back for a UM who wasn't, and left me in coach.
I didn't mind too much since the flight was so empty, but I figure the F/A upgraded the UM since she was less likely to drink any liquor and viewed it as a cust cutting measure.