Jim, Mary, and John,
Jim's blog contains the text of the 8 January 1865 report from "Official Records of the Confederate and Union Armies" series 1, vol. 48, part 1, page 461, regarding the killing of Trollinger and Barton by the patrol of part of Company E, 50th Missouri Infantry.
Another local source gives more information about the incident. I am referring to Jack F. Mayes' 1994 pamphlet "The Civil War in Iron County," published by Mr. Mayes. On pages 6 and 7 he explained that during a larger patrol of this unit while passing through Iron County, some of the Iron County members of this unit obtained permission from their captain to see if they could track down local bushwhacker Samuel Trollinger at some house Trollinger was known to frequent. These six men led by a Strickland were on their way to the house in question when their advance guard of two infantrymen happened upon Trollinger and James Barton. The two Union men in the advance guard fired on the two guerrillas, who were manuevering to outflank the pair when the remaining four infantrymen heard the shooting and outflanked Trollinger and Barton, killing both at no Union loss. Mayes' story gives no precise location.
Bruce Nichols