Board Thread:Morrowind/@comment-120.60.133.214-20130217132959/@comment-5917342-20130226051159

You could try loading a previous save and then go get the cube before Neloth get his hands on it. If you don't want to reload you could try to pickpocket Neloth. However I think it is possible that you have left a cube somewhere else. Go check the doorway you passed by.