2005 Jeep Liberty glow plug on crd

The mechanic removed the glow plug and part of it was missing. I suspect it fell off when he removed it. He did not attempt to find the missing part and he insisted that it will pass through the exaust. Approx 3 inches of the glow plug was missing. He started my jeep even when I told him not to start it. So far there has been no noises but I suspect that it is hanging in there to the side somewhere. Is this possible? Also what do I need to do to remove it? The old glow plug he removed was still shiny at the end where it broke and carbon build up on the rest of the surface. Does that mean it just broke?
The service manager added that the material it is made of is soft therefore it will not damage anything in the engine.