Actually the names and information of dead Union soldiers were maintained pretty well in areas like Deval's Bluff, Pine Bluff, and Little Rock where the Union army had a presence even after the war. In fact the Union Dead in Pine Bluff buried in the City Cemetery were actually moved along with the entire population of that Cemetery to a new Cemetery outside of town on the Little Rock Road to allow for new developement in Pine Bluff right after the War.

It seems that the names were not lost as they appear in the muster rolls of the regiments stationed in Pine Bluff. But when they were disintered to move them to the National Cemeteries, mainly at Memphis, that is when the names became disassociated with the remains. I believe that most of the notations that you mentioned about what the remains were wearing, like a "Cavalry Blouse", would have been made by the recieving authorities as they arrived at the National Cemetery.

Very few of the dead were actually "Lost" the only actul account that I have read was in the journal (I believe) of the 28th Wisconsin Infantry in which the comment was made while on a march from Pine Bluff to the Saline River in 1865, they stopped on the Battlefield at the Mt. Ebla Ferry in 1864 where they had hastily buried one of their dead. the writer remarked that at that time they could not find (remember?) where they had placed their comrades Grave.