Hello -
Several of the soldiers in the 17th Arkansas Infantry commanded by my gg-uncle, then Lt.- Col. John Griffith, were also killed at Iuka. Many of them are buried in a mass grave within the Shady Grove Cemetery (I think that is the name). Am assuming men from the 3rd Texas Cavalry (dismounted) killed during the battle are buried there as well?
I visited the mass burial site/cemetery ~2 years ago now; I don't remember a hospital, but do remember it being right across the road from a housing project/run-down looking apartments. There were a couple of interpretative markers describing the ~250 or so Confederate soldiers buried in a mass grave in the cemetery.
Betting your uncle is probably buried there alongside the 17th Ark. dead....
Hope this hopes some,
y.o.s.,
Kenneth Byrd