The argument to ignorance is a logical fallacy of irrelevance occurring when one claims that something is true only because it hasn't been proved false, or that something is false only because it has not been proved true. A claim's truth or falsity depends on supporting or refuting evidence to the claim, not the lack of support for a contrary or contradictory claim.
I found this part quite funny:
or that something is false only because it has not been proved true
So, someone saying that God doesn't exist because he hasn't been proven to exist is and "argument to ignorance" ?
Or did I read that wrong?
You probably ignored the important distinction between assertion and evidence!