Bryce,

My candidate is Col. John B. Davis of the 15th South Carolina, Kershaw's old brigade (same brigade as Rutherford's).

I believe the brigade was under the command of Col. John. W. Henagan at this time (Dickert's History of Kershaw's Brigade implies Henagan in command during this period although not categorically stated for 27 July). Hess (In the Trenches at Petersburg p.81) identifies Humphreys' and Henagan's units as the advance brigades posted at Tilghman's Gate. The OR (Vol 40, Part 1, p.800) identifies Humphreys being in command (presumably "Gen'l H"). I think it's feasible that Col. Davis may have been commanding the flank regiment and was therefore sent the message by Rutherford.

I can find no definitive proof of this - just a possible scenario.