spark plug engine damage
 

I have a 2016 XC90 purchased late 2015 with 27,000 mls. I've taken it in for all maintenance and never had a problem with it. Driving out of town, the car began to shudder. I was told by volvo that a spark plug had broken and dropped down into the cylinder, ruining the engine. Anyone had this experience of have opinions about how this could have happened?

Is it going to be covered under warranty and would they be replacing the engine ??