Just to post a little more info in regard to the 2nd MSM Cav in the Chalk Bluff area:
I came across a newspaper article from 1880 that gave a short description of the service in regard to several Union regiments (printed during a reunion). It stated that Company H of the 2nd MSM Cav was surprised and 1/2 were captured by Marmadukes men while on their way to Chalk Bluff on April 21st. The remaining men fell back to Cape Girardeau. Marmaduke then attacked Chalk Bluff on April 26th. The Event Records of Company H (2nd MSM Cav) stated they had a loss of 25 men. (Didn't state exactly what loss meant - killed or captured).
By the way, I found the subscription site FOOTNOTE has all of the Missouri individual service cards and Event Records (as well as those from several other states). They are in the process of entering pension records. Pension files of Missouri soldiers are sort of a hit and miss right now.