I've checked all the referenced units but do not find him in any.
The 15th Arkansas was present at Chicamauga consolidated with the 2nd Arkansas Infantry.
George Martin
Joseph McGuire, age 29, enlisted as a Private in Captain F. A. Ragsdale's Company, Walker's Regiment, C. S. Volunteers**, September 16, 1861 at Madison, Arkansas, captured February 16, 1862 at Donelson/captured at Island No. 10 April 8, 1862, sent to Camp Douglas Prison Camp, Illinois, subsequently sent to Vicksburg for exchange, n. d., no further records
**This company subsequently became Company B, 40th Regiment Tennessee Infantry
The regiment was organized in October, 1861, and was composed of one Florida, one Kentucky, four Alabama and four Arkansas companies. It was captured at Island No. 10 April 8,1862; released at Vicksburg, Mississippi in September, 1862, and declared exchanged at Aiken's Landing, Virginia, November 19, 1862. The regiment was called the 40th Regiment Tennessee Infantry and Walker's Regiment Volunteers, but was officially designated the 5th Regiment Confederate Infantry. By S. O. No. 59, Headquarters Jackson, Mississippi, the four Arkansas companies were assigned to the 15th (Johnson's) Regiment Arkansas Infantry, the four Alabama companies were assigned to the 54th Regiment Alabama Infantry, and the Florida company to the 42nd Regiment Tennessee Infantry. The Kentucky company was attached to the 8th Regiment Kentucky Mounted Infantry by S. O. No. 61, Headquarters Jackson, Mississippi, dated October 1,1862.
This company became Company K, 8th Regiment Kentucky Mounted Infantry