Why was i banned?

Hi i was banned this morning for girefing a floor and i was new i was only in this server for one day and no one told me about anything and i put the piece of floor back i Know i am really stupid to do this and i wont grief ever again. Sorry!!!!! i was new only on this server for one day. So i am relaly Sorry!!!!!!! my name is aznduelist is my name on minecraftia so pleases Unban me!!