A few weeks ago I left a quarter on a midtown payphone enclosure. I imagined the coin might stay in place, hidden in plain sight, for an indefinite period of time. FOREVER.

I had good luck with this little game earlier, stashing a dime and then a quarter on a vast stone wall in Queens, recovering both coins in later weeks.

Yesterday I looked for the midtown payphone quarter. It was gone.

That is not surprising. Unlike the aforementioned wall the payphone structure is neither mighty nor forbiddingly high, and while I had to reach up to place the coin on the out-of-reach (to me) surface I would guess that a 6 foot tall human could easily see the shining ducat just by walking past the payphone.

If the coin was not otherwise removed from the surface by wind or apocalypse then I hope I made a tall person 25¢ wealthier.

It is part of my research into where I can safely stash things in urban places where none can see or find them, and without raising suspicions that I am Terrorist.

I started thinking this way as my interest in public signage is revived. Old signs in particular hold secrets, some mundane and others curiously historic, but to me there is joy in finding mysterious signals lurking in public.

I appreciate the unknown and the unanswerable, though I am not a fantasy conspiracist. For me a mystery must start with some tangible physical evidence, something genuine that had meaning which was lost over time.

As a nostalgic child I was interested in time capsules.

As an adult I was chagrined to learn that these containers — packed with the implacable human need to send detritus to the future — are virtually always lost. These ambitiously stocked vessels are stuffed with supposed snapshots of their time. Time capsules are buried or somehow made obscure, intended to be unearthed in 100 years, 500 years, or in 12,000 centuries. Detailed information about the capsules’ locations are supplied to future generations so that finding the treasures will be a snap.

Yet for all the planning and good intentions the time capsules are virtually always lost. Their contents are almost never recovered as intended. Buildings rise up on the once-empty field where an 8th-grade class buried a steel box full of flashlights, baseballs, and sticks of chalk. Centuries from now scraps of paper will surface, the fragile documents describing the location a metal tube full of chocolates, 35mm slides, and one of each unit of coin and paper currency. Treasure-hunting flâneurs will find that the location — once a farm — is a cemetery.

The genre of the time capsule cannot be trusted for historical prescience.

Yet I, for one, appreciate its optimism, aiming as it does to forestall the obliteration of meaningful ephemera. Today’s super-surveillance notwithstanding I see countless quotidian rites and cultural mores vanishing before our eyes, never recounted or passed on. These behavioural evaporations create questions (not answers) for future fascination-seekers.

Some would say that, armed with a favored search engine, there are no unanswerable questions left. I disagree. Until searchies make human consciousness and memory searchable the mysteries endure. Mercurial flashes and inexplicable travels of the mind will continue to disappear into invisible chasms of misunderstanding and beautiful confusion.

There will come a day when even human consciousness and memory will be searchable. Real-time context-sensitive ads and crossing of random thoughtstreams will crack asunder one of the last remaining realms of unpredictable mystery — the secrets of human decision-making processes and subconscious. Initially controversial a “See what other people are thinking right now” widget will be a roaring opt-in success. Mining live human minds for fresh content will be the last frontier and the final fad of the searchies, and they had better get with it before the indexable supply of books, government databases, driveways, public sidewalks, and once-shelved printed matter runs out and the advertisers move on.