Well, from my own particular point of view. Being someone holding a healthy long term eidetic memory. Like I've already told you before. You would have to add to your pot of pondering and scientific examination of the deja-vu phenomenon, the fact that most of us, if not everyone. We are exposed EVERY microsecond to megazillions of stimuli and inputs usually overflowing our senses nonstop. Which, even subconsciously stored & .rar compressed integrally in some hidden corner of our brain, definitely are wiped out and conveniently forgotten from our conscious mind to avoid being overwhelmed by them. But nevertheless, they are indeed there, stored in some place at the reach of a spark of the slightest absentmindedness and distraction outta our attention apart from the events we are witnessing at a given present instant.

Therefore, in my opinion, there is no need to become too religious, esoteric or spiritual to try decipher and explain where those very vivid deja-vu experiences truly come from in our mundane daily life. Those experiences, hunches, perceptions and sensations of repetitive situations and things, affirmatively have been seen, heard, smelled, tasted, felt and happened to us before and are deeply embedded in the core of our inner self. Somewhere in the nodes and connections of those synapses that were built inadvertently and for the same reason not consciously registered and conveniently forgotten. Hence, we are unaware NOW at the present moment that they already previously existed. And we end up thinking that events unfolding before our eyes and in front of our noses at a given moment in the present are brand new. But in fact, they are not. :)