Geoff, yes Laura is buried in Natchez City Cemetery, under the name "Trabue" (and thus presumably unmarried). What I sent you earlier still stands: his widow and daughter are buried in the Inge (her family) plot at NCC; there are unmarked gravesites in that plot; NCC has no sexton (or other) record of Trabue's being buried there; those sexton records were not kept 1863-65 during the Union occupation. In short, the only chance he could be reburied there is if he had been reburied during the war, and the records for that period don't exist.
The only possible solution I could think of would be to try and get the widow's 1917 obituary, to see if (by chance) they mentioned her being buried by her husband. A long shot at best, and a lot of work. Your friend, Bruce