ah, sorry for skipping that! None are factory. It looks like someone may have stripped yours. Depending on why they will or won't charge you, depending on who they will or won't tell you. We never had them from the factory that I know of.
Possibly the spark plug stuck to one, I'd be a bit worried about the condition of threads but stick one in with some kinda locktite, maybe red. And always, -ALWAYS-, use anti-seize on the new plug, to prevent it from sticking to the new helicoil.