I suspect that the recording officer entered these remarks sometime after the muster actually occurred.
George Martin
Private A. J. Cooper, Company G, 154th Senior Regiment, Tennessee Infantry enlisted Nov. 5 or 15, 183 at Missionary Ridge is recorded Present on the Nov/Dec 1863 Muster Roll dated December 31, 1863, under Remarks it is stated "Killed since muster." the Jan/Feb 1864 Muster Roll dated February 29, 1864 also records him Present with the same remarks as before?, he then appears on a Receipt Roll for clothing for the month of March 1864,
Also in Company G was 29 year old H. H. Cooper who enrolled in the regiment June 3, 1861 at Memphis
After Chickamauga, the brigade was again detached from Cheatham's Division to that of Major General Thomas Hindman's, of Lieutenat General James Longstreet's Corps, and the 13th/154th moved briefly to Sweetwater, but returned in time for the Battle of Missionary Ridge on November 25,1863. Then came the retreat to Dalton, where on February 20, 1864, the brigade was again placed in Cheatham's Division where it remained until the end. The 13th/154th remained at Dalton until the resumption of fighting in May,1864, except for one expedition in February to Demopolis, Alabama, and return, when they had started out to reenforce General Leonidas Polk in Mississippi, but were recalled on reaching Demopolis.
From here on the regiment participated in the retreat to Atlanta,the return to Tennessee,and the final journey to join General Joseph Johnston at Bentonville,North Carolina.On April 30,1864,the 13th/154th was commanded by Colonel Michael Magevney,Jr.,of the 154th;on December 10,1864,the 13th/51st/52nd/154th Consolidated was commanded by Major John Williamson of the 51st;on March 31,1865,by Major Marsh Partick of the 154th. [http://www.geocities.com/heartland/hills/4427/13th.htm]