BOB_RR

ok, so i started a world in the void, but after doing so this player (server is set to friends only) BOB_RR joined, but it never gave a message in chat that he did, i banned him from the server, shortly after i left, and the world doesn't exist, is this like a ghost or something? i want to know what the hell just happened to me, oh, and when i searched his username in the searcher where you search usernames to friend people, HE DIDN'T EXIST, the game said error, user not found WHEN I SAW HIM IN MY SERVER, WHICH NOLONGER EXISTS RIGHT AFTER I LEFT, WHAT JUST HAPPENED