wow, what a nightmare! don't know the guy, but that's just plain bad luck. I really hope his recovery and rehab go well.
for everybody up in arms about how this could happen, I can share my perspective.
I've been going to t.hill since 1992 in cars and bikes and I can tell you this is a freak incident. I've never heard of anything like this happening before.
While it's true that one of the reasons that bike track days are relatively inexpensive is that there are not a full compliment of turn lurkers, I can tell you first hand that if he did leave the track after the exit curbing in one, he might have even gotten missed by a full crew, as that is a very unusual place to leave the track......the corner's basically done, unless one were to run wide at the exit, which sounds like that is what could have happened. Also, the start/finish tower probably could not see this occur, as the track is going downhill at that point. Besides, Turbo or whoever is working the start/finish tower would not be looking that direction, instead, the main flagger person is looking down the front straight towards T15 and not looking behind them into one. Even the guy in T5 might not be able to see past the exit of one, as there is a hill between T5 and T2
So if you've never been to a track day or race weekend, don't let this incident make it seem like it's just as unsafe as canyon roads.
That's not representative of the usual experience.
The most important thing is to make friends with the folks pitted around you or if you're lucky enough to go with some friends, all the better.
hope that helps calm the "how could this happen" questions.
Rossispeed in recovery, fr0ng