Oh, interesting. So, hysterical Lambert was able to make a rational decision?
This is definitely straying from what people observe with their eyes. Simply because they're traumatized and stressed, there's no reason for these characters to have missed a very suspicious move on David's part. If anything, they should have been more concerned about what those implications meant straight away. They haven't been on the planet surface for more than a few hours, they've lost five people, they've just coincidentally found evidence of what happened to Shaw and met David who was suspiciously the only survivor. I would think they would see that David was clearly up to something and react as if the situation was getting even more complicated, not ignore it completely.
And also, I'm not buying the Shaw reaction. In all of infinite space they--out of the blue--find where she died after a decade and no one seems at all surprised or curious? Nah. That doesn't work at all.