If they really try, an agent CAN apply a RPU within 24 hours and get you to your rightful spot on the waitlist. I have had this done in the past. I believe it involves unchecking you in and then rechecking you in, and I'm sure a few other buttons along the way. You have to find the right person. This happened to me recently after doing a SDC at the airport and, upon arriving at the gate, I explained the situation to the GA who then unchecked me in and did something that made me #1 on the upgrade list.