This is an issue that you have to see to believe. Please look at the photos I've attached and let me know if you have a solution. Thanks for your help. FYI, I'm using iOS 8.1.
If the problem is just with Numbers:
The part of the keyboard that is missing, could be hidden behind the part of the keyboard that's visible. Tap the dots at the right side:
And drag the keyboard upwards, or downwards to make the missing part visible.