Transmission problem

[Gregs86]

So I came out of the store and started my car while in first gear with the clutch pedal pushed down. As soon as it started it felt like something gave way and the car started to move with the pedal still down. I shut it off immediately. I called my local Vette mechanic he said it was probably the slave cylinder. So had it towed to his shop. Upon further inspection he said something is broken inside the transmission. I did notice days before the clutch would slip very slightly in 5th a couple hundred rpms and then catch. My mechanic doesn’t want to pull the transmission until he sure he can source good parts. I trust him he has 4 zr-1s. I usually do my own wrenching. But was going out of town for work the next day. I’m hoping it’s the fork has broken. So I’m looking for any input. And if anyone has a original clutch disk for sale. Let me know. Car is a 91 with 6200 miles

Thanks Greg