I need help identifying a mystery part.

[Northernsledder]

I just returned home from trailering both of my RT Limited bikes to Florida and back. Upon unloading, I discovered a metallic, threaded fastener laying on the trailer floor. I determined it to be stainless steel because it won't hold a magnet, and it does not scratch easily with a blade. Also, the threaded portion accepts a M5 screw.

Any help is appreciated! I'm not even convinced it's from either of my bikes? Maybe a previously undiscovered fastener from the past bounced from the corners?

Thank you!