On a 2004 ford explorer v6. I had a mechanic tell me the rear timing chain guide went. Upon getting my vehicle to the house I noticed a single spark plug sitting on the front deck on the plastic gutter piece, and looked at the engine to find a spark plug wire hanging free with an empty spark plug hole. They told me they did the work I asked, and had it running, then it began to sound odd and stopped running. Is it possible they screwed up?
It's clearly an issue on their side. A spark plug does not blow out of the engine alone, the spark plug would be shattered at minimum.
Get the best refund you can, reinstall the spark plug and try a different mechanic.
What I don't understand is that you have been able to drive back home like this ?!