Search results are undocked
Search results are un-docked from the Search results window as in the figure. The results appear on the top but where as the search results window is below.
I’m using 8.1.1 (32-bit) version
How to reset this ?
That looks like an artifact of a windows redraw not working right.
You might want to try rebooting. If that doesn’t make the results appear inside their window, you might try undocking the actual Search Results window (below), and re-docking it. If that doesn’t work right, you might try upgrading to a newer Notepad++ (v188.8.131.52 is the most recent version; v8.1.5 was the last before a series of rapid-fire regression-fix versions)