Morning Tom,
It's difficult to follow what you might have done, so, my first guess assumes you were not in the process of customising the view when you mis-clicked, suggesting that you have clicked on the 'splitter', moving it to the top, thus hiding the panes, which, from your description, were 'on top'...
Have a look along the top of the column headings of the file list...
You're looking for two downward facing little triangles as shown below:
Click on one of these arrows as indicated above to lower the splitter and reveal your panes. Depending on the skin you are using, these will be either very easy to spot, or almost impossible. If you cannot see them (They should be in the middle) then you can also rest your mouse on the splitter (NOT the triangles). The cursor will change when you're over it, allowing you to drag it down as far as you would like.
-marko