I looked through my list of TMD field officers and the only two likelies with initials starting with Pr are:
David Provence of the 16th AR.
Clarence Prentice of the 1st division, MoSG.
Seeing as how Reeves' command would have been Missourians, i suspect the order might have been for somebody in the 1st division MoSG arei.e., Prentice's (unofficial) command. A member of some unofficial MoSG unit would be more likely to have not been listed in the Compiled Service Records.