Rob that's true, many men did hide their service records.
I know of several families in North Alabama, with ancestors in the war and assumed they had seved with the Confederacy, only to find out recently that their kin served with the Union. There was alot of Union sentiment in both area's!
Also the John S.'s that I seen, which served with that bunch,served in States farily close to Tn.They where In, Il and West Virginia, it is possible he either traveled North or was drafted or joined one of their patrols passing through the area! I hope this wasn't the case! Even thoughI don't care much for them, Southernor against Southernor.
But if he did serve the Union, be proud that he did what he felt was morally right! You can be proud that he went against the mainstream for his beliefs, and was willing to die for it! Not many people would do that....
I know I'm proud of my kin for this!
Good luck