Maybe I can help you and John unscramble things a bit here.
First of all, although the "old" 5th Cav MSM was originally ordered out of the service on February 4, 1863. This order was later rescinded. The "old" 5th actually was not mustered out of service until June 22, 1863 at St. Joseph.
Bruce, you are correct that there was one member of Penick's regiment killed in the attack on the guerrilla dugouts outside of Independence on February 8, 1863. This was George W. Randall of Company D.
John identified three other troopers in his post: Milton Ewing, Frederick William Falskin, and Jonas Vendeventer. These troopers were killed by guerrillas on March 22 in a skirmish near Blue Springs. The Union patrol was headed up by Captain Horace B. Johnson. The patrol was composed of troopers from the "old" 5th MSM and members of Johnson's own Company L, 1st Cav MSM. Johnson's company had been attached to Penick's regiment in the fall of 1862, I believe. In all, nine Union troopers were killed and three wounded. There were no reported guerrilla casualties. This was, without a doubt, the most crushing defeat Penick's regiment suffered at the hands of the enemy during its time in service.
On another topic, what do you feel can be done to prevent NARA from increasing the charges for Civil War pension files? I would be willing to do whatever it takes to help keep these costs under control.
In the meantime, if I can provide any additional information regarding the "old" Fifth, just let me know. I'll be more than happy to try to do so.