I think your hypothesis makes sense. There were numerous small expeditions from Fort Smith during the war, many of which did not make the OR set. There was a bloody little one in September, for example, that did make the official reports. The muster rolls are probably going to be your best bet because they likely include a summary of monthly events. I have a number of Kansas newspapers from the era on dvd. I'll browse through them and see if I can find any mention for you.

Dale