First, I applaud the OP for rapidly getting off the "DYKWIA" shtick.
The GA had no idea that you recently booked 50 flights and have a million miles. But that isn't from poor training. Or relevant.
As to upgrade protocol, I have to give the GA the benefit of the doubt. The swell around the desk, the circling for that last seat because some website somewhere clearly shows there is a seat left in FC makes for a really tough atmosphere. If the time had passed, and my name was next in the upgrade list and you were a no-show ( and let's be honest, no one is paged only once if they don't show) I would have pushed the GA to give me my upgrade so I could board before there was no bin space left. After all, I have TWO million miles in the program.
Bummer about your foot. But as pointed out, the airport offers myriad good choices for accommodating you, from wheelchairs to the freedom to buy a ticket in whichever cabin you desire.