Try typing /isearch wardstone into the chat window to make sure it dropped. Double check you're running the "normal" version of the dungeon, I know you said normal in your post but it's worth a check. Are you sure you have space in your inventory before you finish? Is there someone or something that appears after defeating the last boss of the dungeon? Sometimes things have to be triggered before you leave to progress further.

It has been a very long time since I undertook this quest so I'm only able to give generic advice. Sorry.