Adjust window is completely gone

I was using the "adjust" window and it was in the way, so I dragged it a bit off my photo - not completely off the screen, but enough was showing so I could grab it. Well, after a while, when I tried to grab it and bring it back on the screen fully, it wouldn't let me. Then it completely disappeared! I tried going to another photo, same thing. no adjust window at all anymore. I can't find it anywhere. I have scrutinized the outer edge of my screen and I don't see even a peek of it. I tried "bring all to front" . That doesn't work. This is so weird. Any suggestions on how to retrieve a lost tool?