Good morning. I find both David and Sarah buried in Nye Chapel Cemetery in Gards Point.
I first find David in 1860 Johnson, Gibson, IN. He was 26, born in England and living with the Edwin C Borin family.
In 1870 Lick Prairie, Wabash, IL [PO Gards Point], David is 35. Wife Lucinda is 28 with Amanda 5, Mary 3 and John 1/2. All listed as born in IL.
1880 Dixon,, Edwards, IL, has David 50, England, Sarah A 35 IN KY KY, Amanda E 15, IN, Mary A 13, IN, John O 9, IL and Lee A 7, IL.
1900 Friendsville, Wabash, IL has Sarah A 63, widow, born Apr 1837. Had 5 children with 3 still living. She was living with daughter Mary A and family. The transcription says Edwin A Baker as husband. I cannot read the original record and I find no records for this family. They had been married for 7 years. Mary had 3 children with all 3 still living. Edwin had to have been married before as there was an older son listed. Thomas E 16, Bertha M 6, Fanny B 3 and Florence A 10/12.
David Fletcher was in the Civil War. His pension application is dated 2 Nov 1883. Application # 498.997 and certificate # 359.209 for IL. Sarah's widow's application # 414800 and certificate # 267897 dated 15 Feb 1890. These records might give you more information.