I've noticed that the Now Bar is cleared from notifications when you swipe down from the status bar and hit clear.
I would think that the Now Bar and the notifications for all other apps should be seperate. When swiping down from the status bar and hitting the clear button the Now Bar should still be there and if you would want the now bar cleared you could just swipe it to the right to clear it.
I say this because I have cleared the now bar by hitting clear and once it's gone I have yet to find a way to get the live notification back up.
