Writing-related medical question

Paging slithytove, porphyrin, or anyone else who would know.

The Ozawa Cup reminded of something I saw at a smaller tournament years ago which I'd like to use in this karate story I'm writing. In a sparring match, a man got punched in the face or head (I was too far away to see the details), hard enough to snap his head back but not to knock him down. The referee stopped the match and apparently asked him if he was OK. The man who got hit seemed to say he was, the ref started to gesture to continue the match-- and the guy collapsed and was carted off by the medics.

Assuming the guy was not faking to get his opponent disqualified, what probably happened? Can a concussion cause you to not lose consciousness at the moment of impact, but thirty seconds later? Also, would it be plausible for a minor head injury to cause you to lose the memory of several minutes preceding the injury-- that is, would it be plausible to wake up a minute or so later and have no memory of the entire three-minute match? Finally, is this probably a check-out-and-release scenario, or would doctors want to keep you at the hospital overnight? (I'm guessing the former just because I've never been in the hospital overnight, even when I showed up after a high-speed rollover collision and the other time when I was given an MRI at midnight to see how far an ear infection had encroached into my skull.)

Writing-related medical question

Paging slithytove, porphyrin, or anyone else who would know.

The Ozawa Cup reminded of something I saw at a smaller tournament years ago which I'd like to use in this karate story I'm writing. In a sparring match, a man got punched in the face or head (I was too far away to see the details), hard enough to snap his head back but not to knock him down. The referee stopped the match and apparently asked him if he was OK. The man who got hit seemed to say he was, the ref started to gesture to continue the match-- and the guy collapsed and was carted off by the medics.

Assuming the guy was not faking to get his opponent disqualified, what probably happened? Can a concussion cause you to not lose consciousness at the moment of impact, but thirty seconds later? Also, would it be plausible for a minor head injury to cause you to lose the memory of several minutes preceding the injury-- that is, would it be plausible to wake up a minute or so later and have no memory of the entire three-minute match? Finally, is this probably a check-out-and-release scenario, or would doctors want to keep you at the hospital overnight? (I'm guessing the former just because I've never been in the hospital overnight, even when I showed up after a high-speed rollover collision and the other time when I was given an MRI at midnight to see how far an ear infection had encroached into my skull.)