A very good mechanic working for me noticed that same piece of hardware with the threaded shaft still in it hanging in the drain hole of an engine and wanted me to OK finishing the work and adding oil. I called the customer who told me that piece had been in there for years and never caused a problem. When I got back into the shop the car was being filled and the mechanic kicked the piece across the floor. While waiting for my to call the customer he got lucky and pulled it out with a needle nose pliers. I gave the piece to the owner who spoke to the mechanic before leaving. At the time I thought that a gratuity might have passed hands but I never asked.