That is weird... If it happens again, I'd go to settings, app manager, look for the Samsung Keyboard and try clearing out cache and/or force-stopping and then trying to use it again.
The keyboard icon you get in the notification bar is another Google-added annoyance in Android 4. You can't get rid of it unless you only have one keyboard installed, and since your phone has two stock, unremovable ones, you'll always get it no matter what. It was meant to easily switch input methods while typing, but IMHO it just gets in the way; it was better when you only long-pressed the text field to get the input change pop-up.