Seeking file containing a letter RE: Removal of charge of desertion (Civil War) - Record group 94.1

In researching the Civil War military service of Simeon Felix Sears, I found this item:

General correspondence with U.S.Military Pension Office https://www.familysearch.org/ark:/61903/3:1:939X-XVXK-9 

The indexed correspondence is not in his pension application file, which makes no mention of desertion and only notes that Michigan can find no record of him. I note this letter was dated 25 Oct 1890 vs his pension application which was filed 4 Oct 1890.  How could I obtain the correspondence related to his request for removal of the charge of desertion?

I obtained his pension application file.

https://www.fold3.com/image/2903357/sears-simeon-f-civil-war-pensions-index

His pension application includes a card 3-216, which under "other claims" lists No. 470915.

Included in the pension file materials is his His Soldier's Application 20 Sep 1890 in which he claims he had applied for a pension about 10 years prior.

I would like to find more information about his service, or lack thereof.

TIA