IN other words, it appears nothing is broken. The PTO shaft is designed
to be "Telescoping". Pick it up, wipe off all dirt and you will see the
male end fits into the female end. perhaps you were sold a too short
of shaft OR, MAYBE, if you did not have the shaft fully connected
to the tractors PTO Stub, maybe it simple fell off!
You probably have an end w/ a spring loaded retainer, did you pull
back and seat the internal setting ball bearings when you connected
it up?
If still stumped post up my pics of the endsa dn everything involved.