Mayan Artefact problem

I have 5 pieces and there is a seperate quest for the sixth it just says find the hidden piece instead of squish zombies tO find them. So now I am stuck looking for the 6th piece because I don't think the zombies drop it I think it has something to do with the episode. For us Britons we may have to download this episode maybe. If anyone finds the 6th piece can you let us know? :mrgreen: