Robert,
That's what I was thinking too -- that they were an independent group -- except that Edwards says they had Minie muskets issued to them at Ft Scott. My guess is that some of this group, perhaps 100 of the 250, were part of Ritchie's undisciplined 2nd IHG that were in camp with their families and the families of their "slaves". (These "wild Indians" owned some slaves but didn't treat them as such.) Ritchie's regiment was made up of companies from several tribes and likely included more African-Americans.

Ritchie may have not reported it because 1) it would make him look bad, and 2) his regiment was disorganized and small bands seemed to wander off and do as they pleased, e.g. the Osage left on a buffalo hunt during Weer's 1st Indian Expedition in June-Aug 1862.

It's possible but unlikely this band was from Phillips' 3rd IHG, which was more disciplined and perhaps, as Keetoowah Society members and entirely Cherokee, was a more cohesive unit.

There was a lot of activity and movements and scouts in the area at the time with both sides trying to figure out what the other was doing so maybe this event got lost in the noise. (Or maybe Edwards completely "mis-remembered".)

Ken