Too late for this transaction, but one thing for you to consider in the future. Take a sharpie marker and make a dot, or mark on a screw head in an inconspicuous place. I'd suggest somewhere on the bottom of the engine. Even if it's black on black, it will show up. It doesn't harm the engine and is easily cleaned off. Most people, even if they see it won't think twice about it.
Take a close-up picture of your mark; time and date stamp your picture. It will help ensure that what you get back is what you shipped.
