you are forgetting the key fact that you made a hypothetical that follows our timeline, in the future
how you fail to comprehend this is beyond me
yes, scientists presume history based on evidence, and where evidence ceases to exist, we enter the realm of speculation - we do not proclaim "stuff didn't exist", just that we can't possibly account for it. that does not mean it did not happen. how "what happened before the big bang" contrasts with "now vs this dumb hypothetical i made up" is that voila we are talking with the knowledge of the past
tl;dr you are conflating with being able to verifiably and scientifically make an account versus "an account doesn't exist"