I also second this. It would be great to be able to disable this behaviour. My prefered behaviour:
1. Ctrl+F -> activates the search box
2. Typing the search pattern and hit Enter -> finds the first occurrence and moves cursor to the text in the file
3. Pressing up or down arrow -> moves cursor to the line above or below the found occurrence
I'm sure there can be other ways to navigate search history without compromising the up and down arrows, for example combining them with ctrl or alt.
it is really a pain to have to use the mouse every time to click on the file to change focus out of the search box. Not user-friendly at all.