Story doesn't mean fiction, it means something that happened.
History has a root of Story, and do you think History is a work of Fiction?
I honestly thought you believed what you read.
Sorry to bring this up again, but I just can't ignore such an atrocious failure to underst basic english alone.
The OP actually specifically stated that this was a SHORT story. A short story is, by definition, a work of fiction:
short story
noun
: an invented prose narrative shorter than a novel usually dealing with a few characters and aiming at unity of effect and often concentrating on the creation of mood rather than plot
But even if it had just said story, the default understanding of "story" is that it can either be fiction or non-fiction, not just non-fiction alone. So if someone says "I read this story once" and goes on to describe a story that is BLATANTLY fictional, you are an idiot to think for even one second that the person telling the story thinks it is non-fiction unless they specifically state that they believe it is entirely true.
Also, does anyone else find it humorous that the guy who is effectively accusing someone else of being gullible is the one who was actually gullible?... Believing that someone else believes that story is practically the definition of gullibility.