Keith, I presume you have checked his Compiled Service Records available through the National Archives and their affiliate branches throughout the country. Also, some local archives have microfilm copies of same like the Georgia Dept of Archives and History in Morrow, GA. These records may have a card in them that lists the Richmond hospital where Humphrey died. Locating the hospital helps narrow the search, but if he made it to a Richmond hospital then there is an excellent chance he is buried in Hollywood Cemetery or Oakwood Cemetery.
John Fox