Hmm, aside from "Hide All Palettes" I didn't think there was a way to turn the Materials Palette off. Are you sure you didn't just completely collapse it? That would like like this and you'd just need to click the "<<" to get it back: Unless you docked it to some other palette than the one it's normally attached to. Still, just look for the double-left arrows above an empty vertical box about the width of a scrollbar. I'm pretty sure CSP won't allow you to drag an undocked palette off-screen, so it must be there somewhere.