I don't know whether Duckworth captured a flag of any kind or not. There was certainly time to burn flags before surrender, and it would be a lot quicker and less likely to be found than a fresh hole in the ground. Witherspoon wrote about 40 years after the fact and was definitely in colorful "storyteller mode" even then. His is the only reference I've found to a flag of the 7th and I don't trust him, especially when there is no substantiation. Sorry to be no help. Good Luck!