And the admin of this forum posted a tip that I use all the time:
http://www.samsung-reality.com/samsung-reality-tips-tricks/unlock-screen-trick/If the screen is black and 'Auto Lock' is set to 'On', press and hold the physical lock key for three seconds both to wake up the phone and also unlock the Lock Screen.
If the phone is displaying the Lock Screen, press and hold the physical lock key for three seconds to unlock the Lock Screen.