A reset is not the
only way, but in order to turn the screensaver back on you would need to be jailbroken.
The searchbar shortcut is only able to turn the screensaver off, but with CLI access -- or one of the KUAL entries in the Helper addon -- you can revert the effects of the searchbar shortcut.
If you aren't jailbroken, then like HarryT said you are out of luck, and you will need to
restart (not reset
) the Kindle every time you want to turn the screensaver back on.