It's possible that someone made the from invisible or even hidden for some
reason. Go to Tools, Options, View tab and check the Hidden objects and
System objects boxes.
Also as Switchboard is pretty far up on the alphabet list, it might just be
out of sight in the database window. Are there any vertical or horizontal
scroll bars in the database window?
On some fool might have deleted it. Drop or rename the Switchboard Items
tables and start up the Switchboard Manager tool. It should prompt you to
start a new Switchboard.