What is it called when an argument is made based on unreliable beliefs regarding extraterrestrial life and lack of evidence?

The concept being described in the question refers to a reasoning fallacy where the lack of evidence is used to support a claim. This is known as an Appeal to Ignorance. This type of argument suggests that if something has not been proven false, it must therefore be true, or conversely, that if something hasn't been proven true, it must be false. In the case of extraterrestrial life, arguing that we do not have conclusive evidence proving that extraterrestrial life does not exist, suggests that it must, in fact, exist, falls squarely into this category.

This fallacy is problematic because it shifts the burden of proof away from the person making the claim and instead puts it on the skeptics of the claim, which is not how logical reasoning typically operates. Instead, a solid argument should provide positive evidence to support its claims rather than relying on the absence of evidence to negate opposing views.