There's another way to phrase that and that is that the absence of evidence is not the evidence of absence. It is basically saying the same thing in a different way. Simply because you do not have evidence that something does exist does not mean that you have evidence that it doesn't exist.
Donald RumsfeldI don't believe anyone that I know in the administration ever said that Iraq had nuclear weapons.
Donald RumsfeldIf a person is determined to fight to the death, then they may very well have that opportunity.
Donald Rumsfeld