I have since discovered, as you probably have yourself, that Ross Macdonald wrote a short story titled "Gone Girl." It seems to have first appeared in a 1991 paperback titled The Name is Archer. The book contains seven short stories by Macdonald. I could not ascertain whether these had been previously published in magazines. The only comment I found on the story was by an Amazon reviewer, who wrote:
Gone Girl- Begins with a burst, then tells the tale of one night of murder in an isolated hotel, and the aftermath the next day, precipitated by a girl trying to escape a relationship with a racketeer.
The fact that "Gone Girl" is only a short story would explain why it is difficult, if not impossible, to find a summary. However, the book itself seems easy enough to obtain. Most of the reviews of the entire collection of seven stories were not enthusiastic. You can find plenty of references to The Name is Archer on Amazon and elsewhere.
eNotes Study Guide on Ross Macdonald offers references to four books in which his life and works are covered. See reference link below.