Pieces of steel in cylinder??

Pieces go crazy inside an engine. My son had a 1/4-1/4 piece of an Edelbrock head valve break off in number 3 cylinder. I had the head off to repair it while he was out of town and for some reason I was under the car and was turning the engine over with a breaker bar. The engine suddenly stopped so I turned it over in the opposite direction and it stopped again. Thankfully I still had the driver side head off so I pulled the passenger side. The piece of valve was stuck in number 6 piston. Thankfully this was a quick fix that could have turned ugly.