Brent: Here is the brief record I have of Joseph Lewis' service in the 1st Division, MSG:

Lewis, Joseph G.: (Cape Girardeau Co.) Age: 26. Sworn into service as Pvt, Co A (Swamp Rangers), 2nd Cav Regt at Jackson on 15 Jun 1861. Horse appraised at $120. Discharged on 24 Dec 1861 at New Madrid. His biography may be found in Goodspeed’s History of Southeast Missouri, pp. 1040-1041.

In light of this service record, I do not believe that he served at Wilson's Creek. At the time of that battle, 10 Aug 1861, Lewis' company was operating in Scott Co, MO, in anticipation of an attack on Cape Girardeau. That attack, of course, never developed, and the units of the 1st Division, eventually retired to New Madrid and later moved to Belmont.