I am not sure on which mental or metaphysical level this kind of disassociation occurs. It may be beyond the biological firmware, in the sense that systems of perception are recording everything with ultimate precision, in a kind of sensory equivalent to raw sensor output. It is not fully processed, as the cognitive system occupies itself elsewhere, with more pressing (and de-pressing) matters. But the data of every moment exists, and we exist in it.
Now, the thing to be learned is to re-associate again, to solely be in the moment. To let the sensory data wash through all of our being, and fill everything with the wonder of the phrase I am Here. To understand and negotiate being there (implying the ontological separation from the world) and being here (implying oneness of perceiving and existing).