I came across some info that the 26th Tenn, was among the Confederate regiments that had broke out and fought. The 26th Tenn claims to have captured "2 flags and 2 small brass cannons". As reported in the OR on Fort Donaldson.
W.H.L Wallace's all Illinois brigade was hit first with the 11th Illinois on the far right. The 11th Illinois did not lose a flag at Fort Donaldson, but did at Shiloh. The 20th-45th-48th all Illinois regiments were also in the brigade with the 11th Illinois. Either one of those regiments lost both flags or that "Battery" of "2 small brass cannons" may have had a flag. Usually the Union had 6 gun batteries. This sounds like a section was captured. I do not know what Union battery this was.
I dont know what happened to the two Union flags once Fort Donaldson surrendered.
Well, that's all I got from the OR report from the 26th Tennessee at Fort Donaldson, Feb 1862.
Have a wonderful weekend,