I had this same issue. In my case I had a bunch of words I didn't want and didn't realize there was the options to reset the learned words. Therefore, I used the system's application manager to clear cache and data. After doing this it broke the ribbon. No matter what I did I could not get it back.
I tried just about everything, but the only way I could get it back was as follows: (please note I am rooted)
1) Switch default keyboard to something else
2) Load "Titanium Backup!"
3) Browse to the "Samsung Keyboard" app and "Wipe Data!"
4) Switch back to Samsung Keyboard and the ribbon is back! :)
I'm not sure why Titanium Backup!'s "Wipe Data!" worked better than the "Clear Cache/Clear Data" from the Android settings menu. I'm wondering if clearing the data from the Android menu a second time would have worked.
I just wanted to post this information to help whoever has this issue next. It definitely can be fixed by wiping the data for just Samsung Keyboard (no factory reset needed). I just didn't narrow it down to if you need Root access, and if you need to use Titanium Backup!