When you discover a system, it becomes connected to the system your scout came from via the space lane it took.
Then, should the space lane and system become unoccupied by any ships (they warped away, were destroyed or whatever), the system and its lane REMAIN connected but are a floating system waiting to be connected up.
That is to say, they are not removed from the board, shuffled back into the "disk deck" etc...
This is correct right? I feel I was confused by the "remove unoccupied, unconnected Star-Lanes" rule in the book, and felt it applied to the systems as well (which i felt didn't make a lot of sense).