I found one of them at the Richmond Confederate Cemetery, Hollywood. I'd have to believe that Renneau is buried there also.
Keene may be there also, or in Oakwood.
Register of Confederate Dead in Hollywood Cemetery [http://www.geocities.com/jbsneezer/]
Ref # Names Co. Regt. State Date Sec No. Remarks Editorial notes
418 Shewmake, H. C. - - - March 24, 1865 X 160 C. S. Navy
STRICT ALPHABETIC LIST: Names in strict alphabetical order