Wow, that's pretty crazy! You must feel good that you were able to get him to the help he needed. You just never know in those situations. I've been involved with two incidents of people getting a concussion after passing out briefly, one in a bike accident and one a snowboarding accident. With both they did the whole nine yards of the ambulance and the tests "just to be safe", and that's really all it was because both people were ultimately fine. But then there are those times when "just to be safe" reveals something pretty major, like in your case.

Yay for you that you were there and took the time to ask if he was okay.