Maybe you have Minecraft open on another computer in your house? The IP that was used to log in matches the one you are currently using to login to the forums, so there is no chance that it was a hacker.
^
Sometimes when you try logging into the server to fast it can cause a glitch and say you're online when you're really not. If it happens again, close your Minecraft and re-open then try. If not, then just msg a staff and they can kick you or something.
Comments on Profile Post by Meme