I installed a pair of headers in my 351 (5.8) Bronco and my best friend was helping me, he dropped a socket inside the down "Y" pipe into the cat, we could never recover it I am sure it isstill there. But that was some hole in one so to speak. Hey kaka happens. I would use a magnet or you might try a rat tail video camera (obviously no
oil in the pan) and see what you can get.
Hope it helps man.
Cheers
Basque1