George, Find A Grave has an In Memory Stone for Richard B. Pittman at Memorial # 87674412 in Walthall County and has his photograph. Find A Grave indicates that his body was at a National Cemetery in contrast to the National Cemetery Administration. At this point in my opinion it's all about sources for the claim. From what source does the NCA use for him being buried in the Thomas Cemetery? And from what source does the author of the Find A Grave Memorial use as his or her source as buried in a National Cemetery? I don't believe the NCA would use Find A Grave for their source. Only after analyzing the two sources could you make an intelligent decision. Some Find A Grave authors are very good while others not so much. At this particular juncture I would tend to lean toward the NCA. Not all of the Confederate dead at Chickamauga were brought back home but some were. If he was brought back to Walthall County I would tend to think it was done shortly after the Battle of Chickamauga.
The Western and Atlantic Railroad was open to the Confederacy at this time period to Atlanta. Was there a railroad that went to or near Walthall County? And if there was did the Union Army destroy and hold the railroad in route to Walthall County Mississippi in September and October 1863 in either Alabama or Mississippi?