Thanks!
I checked the slave cylinder while someone pressed the clutch, and it did everything it was supposed to, or seemed to. The push rod was pressed out, but it didn't engage/disengage the clutch. Now that the clutch is out, there is even less pressure and the slave doesn't do a thing. It doesn't seem to be stuck out, although I guess I could have been wrong.
I said in my original post that he heard a "pop", he said it was actually more like a metallic snap, right over the trans.
Also: I did accendentally yank the push rod out of the slave, while messing around under there...
