Kevin Nash is just as confused as you are when it comes to the match that never happened between him and CM Punk.
Nash was on X-Pac's 123 360 podcast where he talked about his short lived feud with Punk. In retrospect, he doesn't know if it was something that WWE actually wanted.
“I don’t know if they wanted it to happen" Nash said. "When I came back, I had never been there when it was “this is your script and you have to follow it. So I get there and I’m reading his lines and he’s burying me and I have no rebuttals. It’s one of those situations and you know [Triple H] is one of my best friends on earth. I would’ve liked to see what [CM Punk] would’ve done if I would’ve just went up there and just bear pawed him in the face. But Paul [Triple H] was the boss.”
Kevin Nash started off the feud by attacking CM Punk after he won the WWE title at SummerSlam 2011, which allowed Alberto Del Rio to cash in his Money in the Bank briefcase and win the title immediately, much to Punk's chargin. Punk and Nash were supposed to face one another the following month at Night of Champions, but the feud abruptly shifted to a feud between Kevin Nash and Triple H, which culminated at TLC 2011 where Triple H was victorious.