Because he tells MMAFighting.com that he was just hurt too bad to do anything about it:
"The world couldn't see it because the camera wasn't close enough to my face, but as soon as I broke my hand – that was the second punch I landed that knocked him down – as soon as it happened, my lip was starting to tremble, and for two reasons. One, it hurt terribly. I never would have guessed that it was only one broken bone. I felt like all the bones in my hand were, like, entirely disintegrated.... We were on the ground in the second and he was on top of me punching me and he asked me what was wrong. He said, 'What's wrong with you? Why'd you stop fighting?' I told him, 'I broke my hand,' and he was like, 'Bullsh*t.' I said, 'No sir. My hand is broken. That hand is gone.'"
Does his disappearance after round one make a little more sense now, or did you put the pieces together when you saw him in a wheel chair after the submission loss? Or maybe after you saw pics of his broken hand and foot right here. Either way, would you like to see an instant rematch or is it time to move on?