People tend to have a strong sense of the ordinary. Considering what a subjective concept ordinariness is, this seems strange, but, generally, people are aware when something is apparently amiss.
To hide something in plain sight takes advantage of this impulse by coopting the notions of what is “supposed to be,” and hiding something that manifestly is not supposed to be there in its midst.
An Edgar Allan Poe short story, The Purloined Letter, is the seminal cultural example. A blackmailer’s residence is searched from top to bottom by investigators engaged in a desperate search for a sensitive letter. Every conceivable hiding place, under rugs, behind wallpaper, hidden compartments in furniture, even the pages of every book on the premises, has been gone over, to no avail. The story’s blackmailer correctly assumes that investigators will be searching for an intricate form of concealment. The titular letter turns out to have been hanging from a card rack on a mantelpiece the whole time.
Now, there are so many phrases, tropes, and outright clichés about things being hidden in plain sight that it’s difficult to keep track of them all. Yet, it’s still incredibly effective to slip something pass people, even people engaged in a deliberate search, by hiding it out in the open. That’s because making assumptions about what is ordinary dulls the senses.
The immediate leap to find something out of the ordinary is often presented in these types of stories as the product of a limited imagination, which is actually a bit harsh. The search for the extraordinary is more frailty than failing. The drudgery of day-to-day life is hard enough to muddle through without having to pay attention to every seemingly inconsequential detail. Can you blame anyone who wants to find something, anything really, to take them somewhere else? Unfortunately, predictable, mundane, everyday life is exactly where 99 percent of us are stuck. The trick is to make the natural limitations work for you.
In other words, quit being a searcher, and become a hider. It’s more fun, and you’ll get to exchange knowing, meaningful glances with other people who are in on it. What’s the worst that can happen, a vague description of you gets out there: a person wearing denim and a plain shirt? That could be thousands of people; that could be anyone. It isn’t anyone though, it’s you, and no one will ever know.