I would imagine it is undocked and hiding under something. Sometimes unchecking it in the Window menu and then rechecking it will expose it. If it doesn't, you can reset your workspace with Window > Workspace > Reset XXX (XXX=whatever workspace you are using.)
Thanks for this. I didn't get to try it as my computer had righted itself in the morning, so i believe there was some glitch with PS?
Hard to say! I’m glad it’s back though.