This is saying that something is true because there is no evidence that it is not. For example, to say that you haven’t found a partner after years of wanting one, therefore it must be that someone suitable doesn’t exist – although that can’t be proven with evidence, they could absolutely exist but not be either finding or choosing you for many other reasons.
A variation could be, “I’m still single at my age so I’m destined to die alone”, but of course, you can’t logically say that. No matter who or what you are, you could find evidence of someone worse off who coupled with someone. But the retort can always be, “OK, great. My perfect mate exists out there, but if it’s true, where are they?! It’s been ten years!”. The only evidence is this person turning up and they are not here now and so they cannot be presented as evidence. But it’s a flawed argument to say the evidence doesn’t exist because it isn’t here now.
I’M OUT THERE BUT YOU CAN’T SEE ME