MISSING EVIDENCE. “The absence of evidence is not evidence of absence … Simply because you do not have evidence that something exists does not mean that you have evidence that it doesn’t exist. And yet almost always, when we make our threat assessments … we end up basing it on the first two pieces of that puzzle, rather than all three.”(Donald Rumsfeld).
http://en.m.wikiquote.org/wiki/Donald_Rumsfeld