Since it is missing the nut that holds in onto the panel, and doesn't look like any wires have been attached, that would argue for it falling out of something somewhere. Since the OP is the only owner of the trailer, though, and the trailer is five years old, that would be a puzzle. One would think that anything that was loose would have fallen out long ago. If it just fell, the OP should be able to recognize that something is missing. Maybe a mouse is bringing you gifts in hopes that you will let it stay for the winter. <grin>