The batter felt that he didn't swing at the pitch and was walked. When the ump called strike 3 he was surprised and it took a second for him to react. By the time he did, he realized the catcher had already basically retrieved the ball and he didn't hustle it out.
In no way do hitters let up for a no hitter/perfect game. The team is embarassed when these happen against them (rightfully so). However, they also don't bunt to get on to break it either. After the 5th or 6th inning that is known as an unwritten rule in baseball, not to bunt to break up a no-no. I can only remember it happening once against Curt Schilling. Some catcher did it to him in a 1-0 game and got a hit with it, he was not too happy with that fella and I'm sure he got drilled next time they faced each other.