Toggling Fullscreen made my window small and I cant make it big again

I accitendaly pressed F11 (my fullscreen key) and it went to fullscreen. I went to video options and I turned off fullscreen. When I tried to make my window bigger, the size button was gray.

What I wanted to happen was I wanted to go back to my previous screen, but the bigger button was greyed out.

Steps:
1. Open a world in 1.8.7
2. Make sure that the toggle key is f11 (not sure about any other keys)
3. Large screen (NOT fullscreen)
4. Fullscreen
5. Video Options > Fullscreen Off
6. Try to make window big from small

I hope that you guys can fix this!

-RSD94 =D