Student of Medical Science and on going research in Neuroscience.

The reason there's very little scientific literature about 'Mind Pops' phenomenon is that until now we still have very little understanding of normal memory storage and use, let alone the kind of memory that comes out of nowhere. Much of our long term memory is engrained through repetition, habits, facts, or events. The most powerful being emotional cues. There are 2 basic memory processes into long term memory:

A. Sensory information -> Short Term -> (Consolidation) -> Long Term B. Sensory information -> Consolidation -> Long Term

Consolidation is basically all the neuronal activity that mediates the proteins for long term memory. There is an organ in your brain called the Thalamus that essentially works as a filter mediating the consolidation. If you noticed in pathway B there is no movement into short term memory because the consolidation was happened regardless of the short term. This is normally due to the significance of the situation causing us to disregard repetition or recollection in order to achieve long term memory. Emotions can influence this quite well.

I've read in some comments below that some people remember dreams from when they were like 6? I myself remember a dream from when I was 8, not because of the dream itself but how I felt after the dream at the time (I remember feeling a little anxious looking at the full moon after waking up from the dream). But this emotional cue is strong enough to surpass the short term and straight into long term.

Also when we are young, our neuronal networks responsible for memory are the most active and responsive to sensory information, and probably do a lot better remembering events from as opposed to now.

Also we do subconsciously retain information no matter how significant or novel the information is. Our ears are not 'entirely selective'. They are selective in the sense we can drown out noise, but we can still hear none the less. This in itself is enough to allow the brain to pick up information because that is what it is biologically designed to do. Some of this information can also be subconsciously retained, more so when we're young, how exposed we are to it, and how attentive we are to novel stimuli. Still, what we mainly know about memory is based on learning studies and what I'm describing here is not necessarily learning the situation but either observing and reflecting on a situation from which you have retained the sensory information.

TDLR: Brain is weird.