if it smells bad it is the material used for doing a reline, but you shouldnt have been sent home with it. if im wrong either way they should have cleaned it not you. call on monday and have them take care of this.
I am not 100% sure what can be used to remove it. It would depending on the material that they used for the impression also. I know its the weekend now, but I would call their office & ask for specifics.