Craig,
Thank you for the response. I have read Oates' book, but it was sometime ago, and my notes were poorly written. Please keep me in mind if you happen across some definitive information as to how and when the 14th separated from the others for a solo crossing after Van Dorn's army had already crossed. Your theory may be as close as we ever come to an answer to such a small puzzle.
You are truly an invaluable asset to amateurs like me, and I appreciate your indulgence.