One of the reasons that Greathouse was able to surprise and capture so many Confederates with only a 50 man "flying detachment" was because Wrights Brigade was wearing so much Union uniforms the Confederates thought it was some of Wrights men returning from their patrol of the Monticello to Pine Bluff road.

I believe that the wagons that were destroyed by Greathouse at Longview were Wrights train. I would suspect that the flag that you mentioned as being captured may have been in one of those wagons and belonged to one of those cavalry regiments.