Task manager menu, titlebar and tabs have disappeared

"If you double-click the clear border between the task area and the resizing borders, the task manager expands back to it's regular settings.

This is, without a doubt, one of the weirdest features I have ever come across in Windows.

Hope this helps someone from having to finally solve this by randomly clicking everywhere on the window."

This is called Tiny footprint mode and it's useful to keep it always on top with the borders disabled for Administrators with multiple monitors, so they can see more processes and information at once. Albeit I was confused at first too, but it gets handy in the server administration field.