I tend to agree with Andrew, although the reference to the captured flag probably came from a May 1899 address delivered to the Savannah Veterans Association Camp by 50th Georgia commander, Peter McGlashan. The 50th Georgia was one of four Georgia regiments in Semmes' Brigade. McGlashan was temporary 50th Ga commander at the battle and stated in his address to the veterans, "General Semmes fell shot through the thigh and was sent to the rear on a captured Pennsylvania flag." McGlashan would have been in the heat of the action and could have seen the fallen general taken from the field. There were Pennsylvania units engaged with Semmes and Kershaw at the time.
In my research of the 50th Georgia, I have not found any other reference to Semmes being carried to the rear on a captured flag. His courier, William Ross Stillwell of the 53rd Georgia, mentioned in a letter that he helped carry the general off the field. No mention of a flag was made in the letter. No mention was made of the captured flag by Major S.P. Hamilton in his letter to correspondent Peter W. Alexander. Hamilton states that Semmes was "borne from the field in a blanket."
It is possible that McGlashan was correct. I have nothing to prove otherwise. But I have nothing to verify the statement. Without further support one way or the other, we are left to imagine. It certainly sounds more dramatic to be carried from the field on a captured enemy flag.
If anyone can verify the flag story, please let me know. It will be great for the book.