I guess it could be plausible, but since they were outside PH then why would they leave their flag with folks inside or it could be some HQ baggage got left there and when the place was invested it was stuck there. No doubt they had a Van Dorn in 1862 and it probably would not have been utilized after he was gone and definately not with the new 11 and 17 consolidation. Since the unit was in active operations they may have left baggage etc at Port Hudson for safety. They were pretty mobile and probably didn't carry extra "stuff" with them. So it is possible in my opinion but there would need to be good documentation.