Sometimes a software may not handle the resolution, position well and places itself outside of screen, so even you select it you still cant see it.
E.g. Spyder always screws up when the computer switches to different monitors
First, press Alt+Tab to pick the window you want to move.
When the window is selected, press Alt+Space to open a small menu in the upper-left corner. This drops down a menu even the software is outside of screen.
Press the arrow key to select “Move" on the menu.
The cursor now changes to a moving cross.
Press the arrow key to move the software until it appears in the screen again.