Although it's hard to see, I believe the catcher missed the tag because of how he immediately turned around to tag the runner after the runner leapt over him. The catcher then hesitated and tried to make the case that he had tagged the runner on the leap, but the horse had already left the barn when he made the second try to tag the runner.
I've run that back about a dozen times, stopping it at the critical point and I think he caught the ball in the dirt and went up to try and tag but it was his elbow that got the highest, I don't think he got the glove with in a foot of the runner.
That was his third close call on a no hitter in his brief career. Did you see the Yankee triple play yesterday? The hard way... around the horn.