You unpack the clothes the day you get back. The other things take longer. They migrate to the bottom of a bag, then a drawer, then a shoebox, and they stay there for years without ever being decided on.
There’s the transit card, topped up on the first morning, still holding a small unspendable balance for a city you don’t live in. You will not use it again and you will not throw it out, so it sits in a jacket pocket like a passport to a country you visited once.
There’s the ticket stub, folded into whatever book you were reading, now permanently marking a page you’ve long since passed. Half of any second-hand book is other people’s stubs, standing in for bookmarks they meant to buy and never did.
There’s the postcard. You bought it at the counter, fully intending to send it, and then carried it home in your own luggage, which is, if you think about it, the least efficient way to send yourself a postcard. It works anyway.
And there’s the receipt from the meal that turned out to be the best part of the whole trip: unreadable now, ink gone, kept purely because it was there when something good happened. None of it is useful. All of it is evidence. That’s the part we make pins about.