I haven't seen anywhere that the ref admitted seeing a foul and didn't call it. I saw the league said it was a blown call though.

This is a plausible explanation for Wright putting his arms up:

Wright was seen pulling back and raising his arms straight up as Anthony hoisted the winning shot, but the Mavs argued -- which the league's ruling would appear to support -- that Wright was merely trying to avoid a shooting foul once he realized that his charge into Anthony's shoulder on the dribble didn't sway Wunderlich.
"Antoine was so sure he fouled him," Carlisle said, "that he stopped."
The problem I have is why not wrap Melo up when he fumbled the ball at his feet? He wasn't going to get a shot off. Foul him and give them 3 seconds to get a shot off.