Thanks for the note. It's been several years since I submitted my requests to the archives, but as far as I know I would have submitted it with the information I had of at least him being in the 27th US Infantry. His card said Capt. 'J' Van Horn, not 'I' (as in Isaac). I wonder if that created a problem for lookup.
Perhaps I'll try again with this knowledge. The main things I want to get out of this was where he was before the war and where his bounty was.