It is strange that the 6th Texas would be tracking your grandfather in Arkansas after a year, when they were in Tennessee at the time of the fall of Little Rock in September of 1863.

General T. C. Hindman ordered all gunsmiths to be sent to Little Rock for work in the Little Rock arsenal. that order was issued in July 1862.

Company "B" was captured in the battle of Arkansas Post in January 1863 and sent to Prisoner of War camps to be exchanged at City Point Virginia in April of 1863 after which they were joined with The Army of Tennessee never to return to the west side of the Mississippi River until after the war.

I am wondering if the company 1st sargeant, who kept the company records, just assumed the your ancestor was still on duty at little Rock all during that time as they often did with those on sick furlough?

It is possible because of his skills that he was kept at his work for the Federal Army in Little Rock. Or he may have just started walking back home.