Yes, I do, so...we'll go with teeth in a t-rex. I don't know how many teeth they have (although I am fairly certain I could made a pretty close guess using math and Fermi estimations). But, before we proceed, I know about t-rexs, I know they have teeth, that they existed, etc.. I have evidence for all of these things, How many teeth they have is a known unknown, meaning it's something I know that I don't know but that I can find out and make a value judgement on the answer to determine whether or not it falls within a range that makes sense.
For instance, I know that if someone said the average t-rex had a billion teeth at any given time, that number is obviously out of a range that makes sense. If the answer is one, that answer is obviously too low.
The point of this is that now knowing how many teeth a t-rex has or should have at any given time is not at all the same thing as not knowing that something even exists. They are two different types of unknowns. One is a known unknown, something I know that I don't know. The other is an unknown unknown, something I don't know that I don't know. So, lets see if you're going to conflate the two....I swear I've not read ahead, this is a guess on my part that you will.
I told you to pick something you don't know and have not thought about...
Also, you may not think about it after, and use that in your conclusion.