Is it my slave, master, or throw out bearing???

[Cherrybomb]

Alight a couple of monts ago i posted saying i thought my transmission was getting ready to go. Well i found out the truck wasnt running right and theres slop in the rear. Now that the trucks running like a champ i wasnt really worried about the slop cause i have a rear from my 89 and the noise from the tranny has stayed the same no louder no worse shifting actually shifts find until today. Went to work came home left to go get new front tires and all the sudden it got hard to shift then couldnt get it in a single gear except reverse with bad bad grinding. got out checked the fluid. got back in sat there for awhile and pumped the the clutch trying to get it in gear then all the sudden it went into gear every gear fine so what is it? i mean i didnt expect it to do that and i was really pushing the shifter then its just fine? So any thoughts would help i wouldnt think its a transmission internal problem i figure something with the clutch or thow out bearing or slave or master? thanks for any help.