It's should not have done that. There is some amiss in that T19. Not had one apart, but my fear is a snap ring is broken/missing that holds the shaft in the bearing/trans housing allowing it to move. Now the gears are off their normal location and can't move on the shaft........ can't shift anymore.
Will see if I can find some diagrams or rebuild info on the T19 for ya. Post back when/if I find that stuff.
Heath