When I split the text keyboard, that edit bar slips down to the bottom. The formula keyboard doesn't seem to split, but maybe that edit bar is stuck behind it?
On the bottom right corner of all the keyboards are 3 little lines. They are used to drag the keyboard up and down. I would suggest dragging the keyboard up and seeing if the edit bar is down there. If it is, then try dragging the keyboard back down. On the text keyboard, this usually makes the edit bar shoot up above the keyboard.