Like Ingie said, the key will pop up. Search everything and anything -- every barrel, box, bookcase, etc. You never know where something might show up. Using the alt key will highlight things, but won't highlight barrels and chests with things in them, so make sure you pass your cursor over them.
I'm still in Dungeon I of Act IV. I had a bit of a problem when I went to use my Lift Curse skill -- I kept getting knocked out of the game. It's ok now, but it was slow going for a while. I just finished level 1 dungeon and went back to trade off some stuff. I sure miss my Ranaar summoning doll.