Thanks, Jim. That makes perfect sense. Colonel and lt. colonel are used almost interchangeably at times in contemporary writing and AAR's (even when the person in question was commander of a unit organized only as a battalion.)
I'm surprised that none of the studies of Wilson's Creek I've seen so far have filled out the OOB fully. Bearss left off Bledsoe's battery and didn't break down Weightman or Cawthorn's brigades. He also left off the two Home Guard companies that were in support of Plummer. (From looking at Sturgis casualty report it appears the Home Guard were not mauled like Plummer was, and were indeed accounted for separately by Sturgis.) Ironically, the National Battlefield Maps seem to be the most complete way of determining the OOB before digging for each component.