FWIW - The windows hack for bringing off-screen windows back works for this window (and most of the other windows in 3dsMax as well, Slate Material editor, command panel, render settings dialog, etc.)
Activate the dialog so it opens off-screen and has focus. (maintaining the 'focus' is the important part, don't click other stuff after opening it)
Press Alt+Space at the same time.
Then press M.
Then press an arrow key.
Then you can move your mouse and the window should be attached to your cursor.
If you do this to a normal window on screen you can see what the 'hack' is doing....One of those things to file away in memory, it comes up all the time.