The very act of "looking for evidence" moves it out of the category of the absence of evidence. Again, what is being said is, 'no evidence is no evidence'. If

The very act of "looking for evidence" moves it out of the category of the absence of evidence. Again, what is being said is, 'no evidence is no evidence'. If you have the absence of evidence then you have no evidence of absence. We are--kind of--using the word absence in two senses. First as a synonym for none, a number less than one, zero; the second as a synonym for non-presence, non-existence, the lack of an extant sample. Having zero [absent] evidence is not evidence that there is no extant sample [absence]. I hope that helps.