In Firefox, by Ctrl+F a small search box is opened and one can search through the page.
If this box is still under focus, by
ESC on can close it.
But if this box is out of focus (for example if one clicks on some place of the webpage) the shortcut
ESC for closing it does not work.
How to close this search box in this situation with a keyboard shortcut (i.e. without using the mouse)?
To be precise I use Firefox 49.0.1 on Win7.