Sandra Spanier and Brewster Chamberlin discovered Hemingway's first extant short story in a notebook while sifting through other author-related materials located in the Bruce family archives. The story, which was composed in September 1909, is a 14-page series of letters addressed to his parents in which the young Hemingway recounts a fictional trip to Ireland and Scotland.
For more, see Robert K. Elder's article: https://www.nytimes.com/2017/09/29/books/hemingway-first-story-found-in-florida.html.