Someone stole my short story?

What website is it? Because that is not exactly legal, maybe talk to a lawyer? I don't think it will affect your chance of getting published, but if it does hinder it in any way, you could always talk to the website, ask them to take it off because you own the story, and if that doesn't work, I highly suggest talking to a lawyer. Because I mean, it's your story, not theirs, right? :)