Perhaps, in my case in some of these cases I remember wording / sentences explicitly that I can recite from memory, or failing that, I surely remember a string

Perhaps, in my case in some of these cases I remember wording / sentences explicitly that I can recite from memory, or failing that, I surely remember a string of keywords that will only appear in a handful of articles. And like I said, it's not uncommon to find something on Google one day and have it just gone six months later.