I cannot recall seeing the WAB (Work Area Bar) collapsed like that. I would try click+dragging on each "side" to get them to separate. Might be a bit of a "pixel-hunt," but that is all that I can think of. I do not know any keyboard shortcut to adjust the WAB.
If you can separate them, hit the \ (Backslash key), to zoom out on the full Timeline, and then Dbl-click on the little "box" in the middle of the WAB.
Again a pixel-hunt, but you might try Dbl-clicking in the center of the brackets, trying to hit that box, though you cannot see it.
There are keyboard shortcuts to mark the WAB In & Out at the CTI. (I can't remember what the shortcuts are since I ditched the WAB with CS6)
Maybe take a look around the keyboard shortcuts prefs to find it?
I've changed mine to [ and ] but I think they were Alt [ and Alt ] to start with.