Live chat software - Idle / Disconnect detection.
The admin console is able to detect when a user has been disconnected.
If they close the chat session without letting you know, A message will be displayed saying that have closed it.
This stops operators from waiting for a message that may never come.If you feel the session has finished, You can remove it.
However, If the user comes back online. The "status" image next to their session will change to Online and the session can
be resumed.