Surely knowing that you don't know is in itself an admittance of knowing in the first place? At the very least it shows that you know there's something you don't know, so you sort of do know, just without knowing what it is that you don't know (even though you know there's something to know, you...
So, to clarify, you want us to guess how much goes on that we don't know about even though we'll never know what we don't know about, because we don't know about it?