To me, he can only know the greatest degree of confidence in his perceived knowledge of said fact, because of what he believes to be true. There is a part of the brain that simulates previous acted, and sensed behaviors, and if one were to be asked a question, and there is a lapse in what is known as information recall, the brain, having under similar stimuli previously, will do it's best to simulate what response it gave previously. This explains why sometimes we think that a remembered fact is true and we are mistaken.
Dan Gilbert explains in this Ted Talk within the first two minutes. The prefrontal cortex is able to simulate experiences before they happen. I'm not sure as to what "backup" is.
I'm sorry but I still do not understand what you are asking or saying. It sounds as if you are perhaps addressing philosophy of mind, philosophy of psychology, or maybe phenomenology, but the minimal way in which you ask the question, and describe what you're speaking of, leaves me still trying to figure out what you are looking for.
Numerous parts of the brain copy or record information acquired by man. It sounds as though you are concerned with the phenomenon of "recollective memory," but I can't be sure because of how brief or terse your description is here.