Restarted my server.  Got a strange message after it started up.  No players were online at the time.

"IPADDRESS:PORT/STEAMID/USERNAME disconnecting: disconnect"

Server gave no message about someone joining.  Said user hasn't been on the server for at least a week.  Anyone know what's up with that?  Not really a problem; I'm just wondering how that happened.  Can't recall ever seeing a disconnect message before a player joined.
 

Sometimes I see players disappearing on my server without a disconnect message.

I have already seen this and I have not found an explanation or a solution ...