timing chain slapped valve cover.

What is your question?

Backing out of a parking spot i hear a slight bang, not thinking it came from car I kept driving for about two miles. No engine lights came on, soon smelled something hot. I looked under the hood and noticed a chunk of valve cover blown out exposing timing chain. I shut it off towed it home where it has sat all winter. any idea what may have caused this, having trouble finding anyone to look at it.