I'm having a similar problem, when clutch is worked hard or gets hot it disappears.
I changed clutch fluid and fitted an heat shield around master cylinder.
When i tried bleading the clutch fluid through the system the peddle was stopped at floor level, i then decided to swap slave cylinders, new MrT one fitted, still does the same. Next step was to fit a new master cylinder.
Ryan did note this when he was mapping on RR, he suggested i fitted a n/a slave cylinder with more travel.
I'm now thinking my clutch is slipping since it was remapped with more torque and power so the dissapearing clutch is a side issue
Just got to decide which clutch system to get
I've had 2 HKS twin plates and only done less than 5k miles so this time what ever i get will have to work and last.
Its not an easy solution getting a road/drag clutch a bit like suspension systems nothing really does both properly.
Good look with sorting your problem and keep us posted, also well done today with a 10.1 using a knackered clutch, no wondered you didn't do a 1.5/1.6 60ft time and get into the 9's