You want to play semantic games, have at it. The fact of the matter is that this is sufficient justification for us to declare organisms that we know existed to not exist--so it's perfectly justifiable to use this line of reasoning (or logic or whatever you want to call it) to declare bigfoot to not exist.
Repetition doesn't make something true. I have given examples, and others have given others. Please point out where YOU would disagree with, say, my car example. When YOU walk into a garage and see no car, feel no car, and in fact have no evidence that there is a car, is there any doubt in YOUR mind that there is no car? If not, we can dismiss the rest of this argument, because you don't believe it either.
Evidence=data supporting a conclusion. The absence of bigfoot remains counts as data. It supports the conclusion that there is no bigfoot. Ergo, absence of bigfoot remains is evidence of no bigfoot. QED.
Why in the name of all the gods in Hell would I care what HIS credentials are? I'm not studying HIM; I'm looking at the casts. HE is irrelevant for the most part.