The only way that this can happen is if your server wasn't truly restarted, or if you're running more than one server behind a NAT with the same information (then the lobby gets confused)
The lobby doesn't keep any old information. If you stop a server, it will disappear from the lobby in under a minute. If you stop your server and it doesn't disappear from the lobby, then that means you've got another copy of the server running or the one you thought you stopped is really still running. All Soldat servers contact the lobby every 10 seconds, and if the lobby goes more than 25-30 seconds without hearing from a server, it is removed from the list.