Why Was Elijah Coffey not at the Battle of Chicamauga?

The past few days I have been creating a spreadsheet combining all of the dates from the various regimental histories and Elijah's daybook. Today I finished putting all of the daybook in, as well as dates from North Carolina Troops. Comparing the two, there are certain inconsistencies that are incredibly odd, the first being that Elijah was in Kingston Georgia while the 58th fought at Chicamauga. Elijah's daybook and the account in NC Troops are last in sync at Big Creek Gap, TN, however Elijah leaves Big Creek a full two months before the 58th is recorded to have abandoned their positions there. Elijah reaches Loudon Tennessee on June 28, 1863 and seems to stay there except for a brief trip to Bell's Bridge from July 12-21.

The 58th abandons Big Creek Gap on August 22, 1863 and begins travelling towards Chicamauga, passing through Loudon on the 29th. Elijah is still in Loudon when the 58th pass through, but instead of rejoining his regiment, he leaves town on September 2nd and travels south to Atlanta, passing through Cleveland Tennessee, Dalton Georgia, and Ringgold Georgia. By the time of the 58th's first encounter with Union troops on September 11, Elijah is 12 miles South of their position in Dalton. On the first day of the Battle of Chicamauga, he is just leaving Atlanta, reaching and remaining in Kingston until September 21.

The big question now is why was Elijah not at Chicamauga?