I agree, but whatever does exists, exists with or without our knowledge of it.
We can't know that. I understand that you vehemently believe it, but nevertheless, we can't know it to be so. And what does it even matter when we can only know the limited and relatively true/false reality that we generate for ourselves? Why is this so important to you? Why should it be important to any of us?
Why would the unknown road that was available, but not available to Bill, and therefor was not taken by Bill, matter at all? It makes no difference to Bill, whatever, that 'it was there, nevertheless'. He was incognizant of it. And if we are all like Bill, as we all lack massive amounts of information about 'whatever is', what would it matter to any of us? It doesn't even exist except as a vague theory in our cognitive reality.
Do you see what I'm asking, here? What is this current popular obsession with an absolute inviolable "objective reality" that we have only limited and subjective access to, and that therefor remains forever beyond our comprehension? When the only reality that can possibly matter to us is the one that we have cobbled together for ourselves from limited experiences and our imagination, and the one that we are and will always be living in as a result?