Matt,
Good thought. The Loran was mounted at the nav station, not far from the ground cable that all of the other connections are mounted to, so it doesn't make sense to me that a separate ground cable would have been installed (but then, logic does not always prevail). Before recently, I never removed this particular floor board, so unless the connector had previously been connected to something which ran down the center of the boat, accessible at the mast base, I don't believe I disconnected it. If I had, I think I would have investigated where the cable ran to. The previous owners kept the boat at a yard at which the marina was separated from the rest of the facilities by a roadway which until shortly before I bought the boat, had an overhead electric pole line running alongside the road which required that masts be removed every time boats were pulled. So it is possible that someone from the yard disconnected the cable one fall and didn't re-connect it the following spring.
Clark