I wonder about ESP sometimes because two days ago I was thinking about a long lost more-than-a-friend but discarded the idea of writing a message to her last known email address. But today I received an email from her with the words "see you soon, if you'd like." About 8 years since our last furtive contact.
I had a "discussion" with Golden Oldie about this one time (that and her 'distance healing' thing). How many people and how many things do you think about in an average day? Double that for two days and triple for three. There will be common things no doubt, but individual thoughts must number in the thousands, hundreds of thousands or so. It will happen to all of us that we think of someone and a relatively short time later, that person pops up. It is obviously noticeable when it does. But in the meantime, how many people or objects or anything have you thought of that haven't popped up?
Humans are hard wired to recognise faces in anything for example (facial pareidolia), they will also grasp at anything that will bring an order to their world, that's why it is human habit to put people in boxes (rich, poor, black, white, gay, fat, thin, pretty, ugly, forming impressions from job titles or names etc etc). You will have something like a colour, or a car, or an object, suddenly become more important to you for whatever reason, and the reason isn't important, just that it comes, even possible fleetingly, to your concious mind. Something you've not paid much attention to recently - then you start seeing it everywhere or your brain matches it up to a previous thought. At least until your mind moves on to something else. Your brain likes making matches, how many times have you thought, "oh, that looks like....." as it has flicked through its store of mental images to make a comparison.
Your brain, every day, plays tricks on you. We all know this really. It works in the background constantly matching, fitting in to boxes, ordering and sorting, seeing similarities to things you know and can relate to, comparing, dragging up memories (e.g smells triggering a long lost memory) etc etc. It doesn't like the unknown and uncertainty. It will cope by trying to see if anything like that has happened before and will compare it. You are contacted by someone and it will match it to the most recent relevant thought. What if you were thinking of a place but not a person who was there or who told you of it? But then all of a sudden that person pops up? You'd say what a coincidence because you were just thinking of that place - not the person as your brain had a millisecond of filing cabinet search and found the most recent relevant thought.
It doesn't do well with randomness. It likes patterns. When something becomes apparent more than once, i.e. twice or more, it will begin to see a pattern forming and will move the thought more to the front of the brain than leaving it at the back. Then you become more aware of it instead of just some background radiation. As for playing tricks on you, déjà vu/déjà vécu anyone?