This seems to occur in all foobar2000 versions including the latest 0.39a.

Have "Remember windows position" set...
Move foobar2000 window too high to get the part of titlebar over the top screen edge...
Close and run foobar2000 again...
The foobar2000 window is now somewhere out of screen area and cannot be easily got back.

(sorry for bad and simple English )