For years it was assumed that the flag taken was that of the 1st Tennessee (Maney's) - except that it is not. The flag was sent to Wisconsin and loaned to the veterans of the 1st Tennessee after the war for a reunion. When it arrived the vets all stated that is was not their flag - and that the flag that they did carry was actually in the hands of a former color bearer (probably a lot more shot up than this flag is - which I have seen in person a few times).
We now think that it was the flag of the 27th Tennessee that was taken by the 1st Wisconsin. Kurt Holman, retired director of Perryville Battlefield Park also thought that.