[hnfong]

I think "ignoring it" is unnecessarily imputing bad faith.

But ignorance is a thing, even for authorities.

There's a difference between a person/institution having no evidence of X, and no evidence of X in general. So, "who" doesn't have evidence, and how much effort they took to attempt to find evidence before they declared it non-existent, is a relevant question when "no evidence" claims are proposed.

It's funny, because when a person or institution comes out and says "there is no evidence" of whatever (without a context), it would be discredited if any obscure person in the world has such evidence, even if not widely published. It would, IMHO, be much better to say that "we have looked into <all the reasonable sources and literature> and found no evidence" instead.