Is there a law .....?

So I worked for hours making a part for my throttle linkage mount. I was holding it with pliers and sanding it on a belt sander to finish it up when it flew away. Do you think I could find it? No!
This has happened before, working with grinders, wire brush wheels, and compressed air nozzles.
There must be a law that says that this will happen. What's the law?

The "Law" is that those kinds of tools suck your thumb knuckle in and take the skin off down to the bone, so maybe you are lucky and don't realize it.:D