Clutch or 6 speed manual trans problem?
 

Thanks, I need your help. I know this is the S6 forum, but there aren't very many 2.7L 6 speed manual Allroad's out there but this is a more common combination in the A6 model line.
It's my son's car. 2004 Allroad 2.7L 6 speed manual, 157,000 miles, APR chip. Clutch and transmission were previously swapped and have about 60,000 miles on them.
He was driving at about 65 mph in 6th gear, momentarily lost engine power then momentarily regained engine power then totally lost engine power. At the point he first lost power, he depressed the clutch to shift to neutral and coast to the shoulder of the road but the pedal went to the floor with little resistance. After totally losing engine power he coasted to the shoulder of the road but there was a significant drag in coasting presumably engine braking with a now stalled engine. Car was towed home on a flat bed. Now he can't shift the transmission out of whatever gear its presently in. There is no evidence of any clutch hydraulic fluid loss, (brake master reservoir is at normal level and there are no signs of leakage around the master or slave cylinders) but there's little resistance in the pedal. I'm guessing it's something with the clutch fork, clutch pivot or the pressure plate but I'd like to get some recommendations before I get to the point of removing the transmission. Underbody visual check showed nothing out of the ordinary.
With the engine off and vehicle stationary, shouldn't I be able to shift into neutral even if the clutch disk isn't disengaged? I can't understand why the clutch hydraulics could go out at 65 mph when they weren't in use and I can't draw a link between the engine cutting out and clutch / transmission issues. Vag Com diagnostics revealed a misfire (abrupt shock to the driveline?), but this may be a pre-existing code. It's been common for this vehicle.
Your help is greatly appreciated in helping me draw the lines between the dots. Let me know if I left any details out. Thanks