If the clutch was slipping and you kept your foot in it for a while, the heat from the clutch slipping could have done a number of things, for one the friction material could be stuck to the flywheel/pressure plate, stuff in the clutch itself could have warped from the heat, it could have also caused the wishbone to deform so that it won't fully release the clutch (this happened to my SB DD when I let a friend pull the sled).