Pat,
Wittsburg, Arkansas was located in Cross County, Arkansas, and was one of two locations (Wittsburg and Jacksonport)in which all the Confederate forces assigned to the Northern Army, Sub-District of Arkansas was surrendered by order of General M. Jeff Thompson. While most of the Confederates were not "captured" per se, they were, as members of a surrendered force, officially considered and treated as Prisoners of War. Each soldier was ordered to report to the closest site to be officially surrendered. Each soldier laid down his arms (if he had any), and waited until his parole paper work was processed. L'Anguille, as I understand it, was located in St. Francis County, Arkansas.
After Price's Raid into Missouri, Dobbin's Regiment had been sent back home to recruit and re-equip. It is possible that some of the members were furloughed until ordered back into service. apparently this is why Dobbin's men were surrendered/paroled at Wittsburg instead of Jacksonport. i hope this helps.