Thanks Clifton, I think I figured it out. Me and a friend were installing the rear motor mount, header and exhaust a few months ago. It looks like it's the factory rear motor mount fastener. The CP-e came with new hardware so the this is probably the original.
I was a little freaked out when a piece of hardware that size fell from the inside of the skid plate. I searched the engine compartment and under carriage throughly and I can't find anything missing.