It was plain obvious why the Luna sample was sought so bad when the first guy died of the virus. With all the impossible amount of water pouring out of him, and the indications that all previous station members died of drowning, together with the shortage of water on earth and no radiation on the station, they all couldn't put two and three together.
Also when the obligatory fifth column guy put the sample in the box to take them away and was caught; his explanation was that the captain asked them all to meet at a location. Yet, our two not so smart experts who walked in on him didn't feel it to ask the captain if this was true?