In the "Roll of Prisoners of War of Louisiana at Various Places, on file in War Department, Washington, DC, Copied by T. W. Castleman, Commissioner of Louisiana Military Records", located at Jackson Barracks, La., in Misc. Book 3 there is a Private S. Coutz, Co. D, 2nd La. Cav listed. He was captured near Natchitoches on March 21, 1864. Chances are real good this is the man you are looking for, given that a script 'z' and a 'y' are not very different. (The list available is a typed transcript of the original.) He was "sent to Red River Landing, July 22, 1864 for exchange. Exchanged July 22, 1864." Nothing in the record indicates that he was dead at the time, and there are several on the list who are noted as having died in captivity, along with their date of death.