In Asimov's Galaxy, the Good Doctor writes:
But I haven’t read every story ever written and many that I have read, I have completely forgotten, at least consciously. What if I duplicate important elements of stories I have never read or have forgotten? It’s possible. I once wrote a short-short which ended with a certain dramatic climax in the last sentence. Eventually, I received a letter from another writer whose story had been published before I wrote my story and who had made use of the same dramatic climax in his last sentence. What's more, I had his story in an anthology in my library. I did not remember reading it, but I had had the opportunity to do so. The two stories, except for the climaxes, were completely different, but I promptly wrote the other author and told him that although he had my word that there was no conscious imitation, I would withdraw the story from circulation and it would never again appear in any anthology, any collection, any form whatever—and it never has.
Presumably, as almost all of the rest of Asimov's science fiction output has been anthologised in some form or another, it should be possible to deduce what this story is. What is the missing story? And, if it can be ascertained, what is the other story with a similar ending?