If my suspicions are correct, this is a windows problem and not a psychopy problem. This used to happen on a windows machine I used with different applications. Try the advice in the link below. I'll quote the relevant parts here in case the link ever goes dead:
Getting Your Hidden Window Back with Cascade Windows
The easiest way to get back a hidden window is to just right-click on the Taskbar and select “Cascade windows”.
If that doesn’t work, proceed with the keyboard trick below.
Getting Your Hidden Window Back with the Keyboard Trick
There’s a simple trick to get around this. First make sure you’ve
alt-tabbed to the window, or clicked on it once to bring it into focus.
Then right-click on the taskbar and choose Move.
Note: If you’re using Windows 8 or 10 you might have to hold
down the SHIFT key before right-clicking in order to get the Move menu
item to show up.
At this point, you should notice that your cursor changes to the “Move” cursor, but you still can’t move anything.
Just hit any one of the arrow keys (Left, Right, Down, Up), move your
mouse, and the window should magically “pop” back onto the screen.
Note: For keyboard savvy people, you can just alt-tab to the window,
use Alt+Space, then M, then Arrow key, and then move your mouse.