I found this story in the newspaper Central Register of Kosciusko MS; you can see a clipping here. To summarize: Mr. James Davis of Bibb co. AL, married to a daughter of Mr. James Moore. In about 1835, a man visited the home of a Mr. Raifield of Bibb county, bringing with him an infant boy, and stayed the night. The next morning the man was gone but the baby was still there -- along with the child's clothes, $50 cash, a horse and bridle, and a note requesting that the child be named Gordence Garriston. Mr. and Mrs. Davis adopted the child, whom they called John Marshall, and Mr. Jesse Beene (who wrote to the paper) stated there was great affection between them and the boy.
I believe I have located the family in the 1850 census:
"United States Census, 1850," database with images, FamilySearch (https://familysearch.org/ark:/61903/1:1:MHPR-KH2 : 4 April 2020), John M Davis in household of Jas M Davis, Bibb county, Bibb, Alabama, United States; citing family 503, NARA microfilm publication M432 (Washington, D.C.: National Archives and Records Administration, n.d.).
This will no doubt be of great interest to any descendants of this boy. It is, of course, interesting to wonder who the boy's biological parents were. The man who left him with the Raifields was likely his father, or an uncle, or perhaps a close friend of one of his parents. As he was young enough to still need nursing, he could not have been brought very far, and must've been born in one of the surrounding counties of Alabama (Bibb is almost in the center of the state). As the man brought a horse, he didn't float down the river, he must've ridden in and then departed on foot.