After the Civil War, the Union soldiers were moved, for the most part, to the nearest national cemetery. This
happened around about 1868. For the most part, those men have marked graves. It is possible the surname was
altered some way or even lost. So he could be under a Unknown USA, but more than likely, there is a surname on the
marker that was placed on the grave.
I would suggest you post down in Tennessee asking where-the site-those men were moved to. Take my word for it, the Union
Army marked their graves.