Once when you were on holidays, you saw another tourist who you forgot almost instantly, but who remembered you for the rest of their life.

It wasn't anything you did, not really - a coincidence of light and position, mood giving you form and your summer clothes telling everything of your life. Though the tourist said nothing, that moment captured you so perfectly they felt they instantly knew you. They suppressed an instinct to wave or nod, and turned away, but turned back again almost immediately doubting themselves. You noticed this double take and looked back at them, curious, but they looked away again. That was the entirity of your interaction.

Over the subsequent days they realised that this moment had been a confluence, the collision of two waves in the ocean. They were in the precise mind state to perceive you and you were in the precise state to be so perceived. They understood then how love at first sight was possible and regretted not talking to you. Haunted by curiosity but paralysed by propriety they waited too long to have even a chance to reconnect, and returned to their country where they never talked to anyone of this realisation, and had regular dreams in which they talked with you and told you of their life.