Ok I found the record you referenced in Fold3 for the 15th MO Cav service.

The real question is this the same person that appears in the 2nd Colorado Cav?

what do we know:

Milford H. Sanders enrolled age 35, March 13 1862, Pocahontas AR by Capt turnbull into Timothy Reeves Company 15th MO Cav. for 12 months.

He is on detached service to recruit with Capt Cunninngham in MO May to August 1863 now listed as enlisted Aug 1862 for 3 years or the war.

He is next found recruiting with Timothy Reeves in SE Missouri Sept 1863 to Feb 1864. The record goes cold there. https://www.fold3.com/image/92794841

Next we have Milford H Sanders listed in Co K, 2nd Colorado cross referenced to an alias Milton H Saunders https://www.fold3.com/image/320169484/

Following that record we have 24 pages records including an enlistment certificate into 3rd Colorado Infantry Volunteers (later merged in 2nd Colorado Cav) with both names ascribed done at Pilot Knob, MO Oct 1863 with an age of 38, 10 months with his nativity specified as Spartanburg District, South Carolina. https://www.fold3.com/image/320169870

He was immediately detailed as a cook. Oct to Dec 1863. Feb 1864 finds him sick in hospital at Dresden (Pettis County MO). Nov 1864 through Mar 1865 finds him assigned as Company Teamster. He is subsequently discharged at Ft. Leavenworth Sept., 23 1865.

So after looking at time lines we have an overlap from Oct 63 to Feb 64 in these two records which would normally be considered excluding the two being the same person. Clearly the 2nd Colorado fellow is likely the same guy in the 1860 Reynolds county census as his nativity in S.Carolina is clearly recorded. This overlap does not preclude the two being the same man but would indicate that he would have left Tim Reeves command and "deserted to the enemy". Reeves was later involved with the Wilson affair in Ripley County in Dec 1863. He was not one to lightly forgive those he considered an enemy. I guess stretching the imagination a bit was MH Sanders a planted spy for one side or the other? Good luck with your hunt.

John R