Many years ago in a shop I was working at a cylinder was getting replaced on a Cessna 206. Often, while the cylinder is off the mechanic will put a shop rag under the connecting rod so it will not rest on the case. Well, over the weekend, the owner of the plane came by and decided he wanted to dress the gravel nicks out of the prop and in the process of turning the engine over the counterweight of the crankshaft pulled the rag inside. When the mechanic returned to install the new cylinder he was a bit miffed that his rag had disappeared but I guess he just blew it off as one of the mysteries of the universe like when socks disappear in the dryer. Anyway, that plane never made it 300 hours, it did manage to make it all the way around the pattern on the first test flight though and landed safely.