This has happened probably to everyone that uses SSH from time to time. You logged in to a terminal over SSH and your session is stuck (e.g., no response). Most people will kill the window or the process that runs SSH and open a new one. There is actually a way to recover from a stuck session and it is quite simple:
On the moment your session is stuck, you press tilde + dot (shift "~" + ".") on your keyboard to send a break sigal. You'll end up at your own shell from which you can resume the session by opening it up again.
Got this one from the RedHat network.