The 56th Georgia was not in Atlanta in July 1862. It had been formed 15 MAY 1862 and was part of Leadbetter's Brigade, Heth's Division, Deparment of East Tennessee (JUL-OCT 1862).
If you have not obtained a copy of his Compiled Military Service Record (CMSR), then that would be the first place to check. Often times it will have where the family filed with the county clerk's office to the Confederate Government for the balance of the soldier's pay and allowances.
The Georgia Regiments formed during 1862 were hit severely with disease. So much so that General Kirby Smith requested that that Governor Brown fill the ranks with conscripts because many regiments were at about 30% effectives.
Private William R. Michael died on 29 JUL 1862 of "Febris typhoides" or typhoid fever. He is shown in the records of Heery Hospital, H.W. Brown, surgeon (these are separate from the CMSR's). Reports of sick and wounded soldiers, Jul-Sep 1862. This entry in the records were part of the records of Dr. Samuel H. Stout who was the Chief Surgeon of what would become the Army of Tennessee at the time. This hospital was in Atlanta and built on the Fairgrounds. Later in the fall it would be named Fairgrounds Hospital #1. The Fairgrounds today would have been located just south of Memorial Drive and Hill Street is today. His records are all over the place but these are in Record Group 2G384, University of Texas. Your soldier's note was a single line entry.
It is possible that he is buried in Oakland Cemetery but I did not find him in the rosters. It is also possible that he was taken home if his family was aware of his death. He was in Company I, 56th Georgia which were men from Carroll and Coweta Counties. These counties were easily accessible by rail and the body could have been moved quickly. Summer time in Georgia, heat, and dead body was not a good combination. It is possible he was initially interned and the body later retrieved by the family due to the proximity.
I hope this helps. Please let me know if you have any questions.
Gerald D. Hodge, Jr.
War Between the States Historian
Historian: 39th Georgia Volunteer Infantry Regiment