Processing seems to recall the window position, which I've noticed can be a problem if you drag a window to a second monitor, for example, and later don't have the second monitor connected.

For "lost" windows, you can try using keyboard shortcuts to initialise the "Move window" feature (supplied by the operating system).

Alt + SPACE (to access the window menu), Move

Then you can use arrow keys to move the window. Try holding the left arrow key for a few seconds and see if your missing window appears from the right side of the screen.

-spxl

frame.setLocation(int x, int y);