Wow. I'm shocked, stunned and dismayed.
This didn't happen at one of my track days but because all the track day companies rely on Thunderhill to provide the trained and experienced workers this could have happened to anyone.
I hope Sami's pit mates talked to the organizer as part of their search for him. I know the only time something like this happened at one of my days (someone was missing for 10 minutes), we immediately shut down the track, started rolling the ambulance, etc, only to discover that the missing person had parked at one of his friend's pits further down the paddock. I was shocked that day, too, because I couldn't imagine anyone having an off-track incident that was not seen by a worker. We (and all motorcycle track days) have workers staffing start/finish, T3, T5, T7, T9, T11. From those turn boxes you CAN see the entire track. Where Sami crashed IS an extremely unusual place but we have had mechnical breakdowns coast to stops in pretty much the same place without losing track of them (they can be seen and monitored from the T3 station).
Since I read about this incident this morning I've been really thinking hard about how this type of freak incident could be avoided in the future. When I say "freak incident" I really mean it. Between us, the major and smaller track day organizers literally have provided service to thousands of days and hundreds of thousands of riders and I've never heard of an incident even close to this before now.
But we're in the business of providing the safest environment for motorcycle testing and education so we need to plan to avoid this type of incident. I've been thinking hardest about how to improve the on-track staffing so that no-one could ever slip through the net again. Putting a worker in the T1 box is an obvious requirement. A worker in the T8 box would help remove what I now (with hindsight) see as another potential blindspot.
Thoughts about additional locations? I will distill these thoughts and communicate them to Thunderhill.