Hello. Is this in Language and Input.
Can you reset it there.
Do you have a setting for Default Applications.
Try Applications Manager - All - Samsung Keyboard - touch for App Info - Enable
or Reset Default Applications which used to be in the Task Manager or Recent Applications button, then Menu - Reset Default Applications.
My memory of Samsungs is fuzzy.
Also go to Safe Mode (Off - Volume Down - Power and Home buttons together Safe Mode start, then restart normally. It often brings back stock items.
Also try SwiftKey keyboard and toggle back to Samsung keyboard if you prefer that.