I wouldn't give a rats abt reimbursement for the cost of plug replacement. My concern would be did a tiny bit of porcelain get into the engine when the cracked plug was removed? Porcelain is great for machining steel and I have seen an engine destroyed by a sliver of porcelain inhaled down the plug hole.

 

Interesting thought but I am sure there would have been indicator if that happened. You and I, pretty sure have seen many solid objects and parts get into a combustion chamber and most get shot out the exhaust system. The other get stuck pretty much permanently in the head dome or top of the piston and most other objects get stuck and never cause any problems. But always entertaining when you tear an engine down and find them and wonder what the story was. LOL
Trust my owning an engine machine shop I may have seen it all. LOL

Besides I am still with the firm theory that the spark plug was cracked during removal and not while it was operating in the cylinder??

 

Yes I agree. If it were running cracked it would earth out and log a misfire code.

 

Most of the time but not always. I have deliberately cracked a spark plug and run it on an oscilloscope just to see what the wave pattern would be. And it’s actually had to tell unless you run the rpm to 3000 or more. So technically it would not cause a DTC and could go un-noticed in normal daily drying form hundreds of miles or more before showing indications of a weak cylinder.