Didn't see this one on the list, but on the second mission "the walls come down" where the hive spawn when u have to examine the the big siva crap, there is one on the under side of the bridge. It'll be the bridge right before heading to refinery(?). Like if u stand on the circular thing right before heading to the refinery(?) and look at broken bridge thats near it. Itll be on the under side of it. Its a pretty bad explanation sorry xD