Usually the player name will be stored locally, at least if the client was able to connect to the hive in the past. But multiplayer servers reject players if there is no connection to the authentication server (this behaviour can be disabled, as mentioned, but it's not recommendable).
This did not work for me yesterday. I play on Exxter's server, and he had set server_hive_verification=false. He could play with his normal character whereas I could only play as Unknown User. I suspect this was because he was authenticated by Steam whereas I was not.
But anyway thanks for restoring the service. We have to take it as it comes