hello, and welcome. I have had a similar problem with an older vehicle, it was an 85' pontiac Grand Am 4 banger. However the ceramic plug insert came out and the threaded metal end stayed in the head. That thing took me to 363,000 miles. If you're plug is intact and it came out of the head, whole, then I would say that you my friend , have a problem. However, you said the number 4 plug, what engine do you have?? 4- or 6cylinder? It is possible to maybe tap the head ( you would need to most likely remove the valve cover first for easier access) with a slightly oversized tap. If you're going this route I would suggest that you first tap out the spark plug hole with the same size thread first. Then install a new spark plug carefully into the hole. I'm hoping that you don't have the bad plug on the inside bank (closest to the firewall) of the v6. That requires a whole lot more work and nasty words.
good luck, there's plenty of help here if you need it.
Jim
