Help!! reconditioned gearbox install muck up

I have a Ford Courier PE 2000 2.5 TD
I received my 'new' reconditioned gearbox and started putting it in today when it all turned to manure.
Whilst I was placing the sender unit for the 4wd light, the larger sender forward of the transfer case, the metal contact bullet that needs to be slide in, fell into the box. the rear sender for reverse is no problem at all as it buts up against the plate inside the box.
Im confused as how it slide past the backing plate, but regardless it now lies in the box. My options are to rattle it around in the hope it can pop back out the sender hole - heavy unit to shake like a money box. OR send it off again to have it cracked for the removal of the bullet.
Has anyone had any similar experience or some advice?
Thanks