Just tow it off the track and put it next to a concrete barrier before you call and report it
...then blame VDC for being off
Will there be professional instructors at this event providing free instruction? At this event or group you are running in: do they not allow passing in corners, is the event not timed (i.e. no prizes or places), and will there be instructors on site? If yes to all those, then they may qualify the event as driver education and cover you.
I was at Willow Springs a few years back and a girl put her brand new SS camaro into a wall. The car was totaled, she and her passanger were fine, but her insurance did cover the cost of a replacement vehicle because all of the above conditions were satisfied.