How to get back a windows out of the screen ?

I had my friendfeed window going away from my screen... my mouse was released, but the window continued to follow it... and it gone away ! I can't manage to find it again, I guess because the app is remaining where I put nativeWindow last session to recreate it at same place...
Where are stored this informations ?
How can I reset it ?
Maybe it would be cool to add a simple option to reset windows size and position :)