Just passing by and taking a look at interesting questions, I don't think your answer deserved one star. I don't know any of the participants in this thread, but might have a guess about how it happened.
In the display of an answer and the clickable buttons for ratings and the clickable button for "comment on this answer", notice what is right next to what. It's almost like a PC having the "backspace" key right next to the "enter" key, so easy to hit "enter" and commit the error that you were trying to back out of. But not quite identical, because even if the user's fingers work right, the web page depends on the mouse's rollers not glitching in the instant before clicking, and you can surely guess why I'm aware of mouse rollers glitching.
Anyway, if I had the question involved here, I would surely have posted a followup saying what the situation actually is, whether it matched your guess or not. Or more precisely, I would surely have posted a followup unless the click accidentally landed on the one-star button.