Clutches don't get stuck away from the flywheel. If the engine is running and you can put the truck into gear without pressing on the clutch, and the truck does not move... seems to me you either have a clutch disc with a seperated hub, or a broken pilot shaft. Either way, it is time to drop the transmission and have a looksee. It is fairly common for the clutch discs to shatter, or for the rivots to shear off the disc.

John