I read this humorous short story in a SF&F collection, more than 20 years ago. I am positive is it by a very famous SF writer but I forgot whom.
It is a fiction, but in a world that, alas, could very well be ours. So technically, neither SF nor Fantasy, but because of its author and the decision of the editor to publish it (and this was a collection so probably it had already been previously published in an SF&F magazine) I consider it is "on topic".
It is about a SF writer telling to his friends, just for fun, having first claimed he was a expert on the field and present at the event, a totally harebrained story about a nuclear reactor gone critical that instead of exploding, has created an antigravity field around it (the "anti-gravity" tag does not exist, so I used the "artificial-gravity" tag instead).
Unfortunately for him, some crackpot heard him, and believed that his story was true rather than a joke. So his story was published in one of the many pseudoscience publications, mentioning his name and calling him a reliable authority, an "expert" who had personally attended the event.
So he kept receiving an avalanche of letters, some calling him a liar and pointing out the many scientific inconsistencies, but most of them be "believers" who wanted more details.