Ever gotten money back from a machine shop?

Sorry, leaving plugs out is engine building 101. When I did engines I always put oil in them and hit them with a primer and gauge before they went out the door. Still you won't get anything back, how does he know you're not making things up. It does happen. Once that motor is out the door you just don't know what people have done to it. Like said above, you would have needed to let him figure out how he was going to handle the issue.