Or, have you not taken a look at its listing on your submission's page recently? If a story is rejected it will just mark that there. You won't receive any other notification. A story (unless its an audio or illustrated story) should post in five days (my last one posted in four) currently--a bit longer maybe for new authors. But if you've gone ten days and haven't fiddled with anything on your submissions page and there's no rejection notice there, you are justified in asking the site editor, Laurel, directly. You can contact her via the private message (PM) system at the top right corner of this page.
"I don;t spend time checking on what other people are doing, I just worry about my own shit."