As you stated, The muster roll for Aug 31, to Oct 30, 1863 states that he "Died from wounds received in battle of Chickamauga Sept 20, 1863."
His name also appears on a Register of Officers and Soldiers of the Confederate States who were killed in battle, or who died of wounds, or diseases. When desceased Sept. 20, 1863. Where and from what cause, killed at Chickamauga. Effects received March 14, 1864. At the bottom of the card it states: This register appeears to have been compiled in the Adjutant and Inspector General's Office from returns furnished by hospitals and by Regimental and Company Officers.
His name appears on a Register of claims od deceased Officers and Soldiers from Alabama which were filed for settlement in the Office of the Confederate States Auditor for the War Department. Presented by Elizabeth Floyd, widow. Dated May 2, 1864.
What is not in his file is a Register from a hospital with his death information. While not conclusive, it can be reasonbably determined that he was not admitted to an organized hospital beyond the battle area. If he did not die on the battlefiled on the 20th, but wounded on the 18 or 19th, he may have been at the Regimental fieid hospital when he died and buried nearby. His Regimental or Company Officer supplying the return to the Adjutants Office as noted above. If an attempt was made to transport him to a hospital elsewhere, he could have died in route and was buried whereever they found applicable. If he was taken to a local home or church that was used as a makeshift hospital and died there, he could have been buried there. The possibilities are quite a few.
What other accounts have you seen that make you believe he was not buried on the battlefield?