Here in rural Virginia it is not uncommon to have an old family graveyard on your property. We found this one buried in the woods on the far back corner of our land. No trail or road to it, obviously lost to memory. Lot's of history here, unfortunately we can only ponder.
Have you asked the county if they know anything? A few years ago our county, I think volunteers did the work, mapped all of the small graveyards that could be found. I knew of a small family plot that was from when NC was a colony and was in a very remote location. Even today that place is kinda out there and back in the 1700's it was frontier. When I heard the county was mapping these old graveyards I sent them and email about the place I knew about and they already had it located.
Not sure if they had anymore information about the graveyards though.