It happened again recently at the Cyndi Lauper concert.
I was making my way to the washroom and she was just strolling into the stadium with her boyfriend, perhaps even her husband, when we saw each other.
Our faces were impassive; they did not show any sign of recognition. But our eyes betrayed the fact that we knew each other.
Oh yes, I know her. Her name is Anne and we used to be in the same sociology tutorial class in the National University of Singapore.
I wouldn't describe us as the greatest of friends, but we had traded essays, notes and chatter outside Lecture Theatre 9 and in the corridors of the Sociology Department.
At the Harbour Pavilion, Anne and I held each other's gaze and read each other's signals. We were people caught in a dilemma; we were both hesitating and wondering: "Should I say hello?"
We made our decision in a split second. No. And simultaneously, we both looked away.
It was not the first time I've played this game of pretence with people I know. Perhaps both Anne and I just wanted to avoid the awkwardness of having nothing to say. Time, after all, has a habit of stealing familiarity from those who once hand many things in common.
I did not lose sleep over the episode. After all, while Anne and I got on well enough, we were really not very close.
I am, however, disturbed by a similar encounter with a childhood chum in Kuala Lumpur recently.
I was enjoying a bowl of beancurd at a roadside hawker stall when he strolled up with two little girls, presumably his daughters, and asked for three glasses of soya milk.
I hadn't seen Ah Fatt in at least 15 years.
His once reed-thin frame had bloated and he looked blimpish but I knew it was the same guy whoose mother had the largest collection of Chan Poh Choo -- a big '60s Hongkong movie star -- records in the neighbourhood.
He knew who I was too, I could tell from his stare. But neither of us ventured a smile, let alone a hello.
What prompted us to treat each other as strangers instead of friends, I do not know.
I just find it strange that two grown men, virtually inseparable when they were children, should be at such a loss for words.
I do not know if he was self-conscious about the different path we had taken in our lives -- I had gone on to university and become a journalist; he dropped out at Secondary 2 and is now a mechanic -- but it was certainly not snobbery that stopped me from acknowledging him.
I knew I wanted to make contact; I just didn't know how. I think he felt the same too.
The reluctance to renew ties is puzzling.
After all, I sometimes think nothing of accosting and interrogating familiar-looking people with: "Hey, do I know you from somewhere?" Or jabbering animatedly with people whose faces I've almost forgotten.
A friend, a pseudo-psychoanalyst, thinks Ah Fatt and I might have been afraid to discover we had nothing in common if we re-established contact. So, rather than risk becoming awkward friends again at best, my friend said, we would rather be strangers and keep our memories.
It was an intriguing proposition 00 melodramatic and romantic even, but far-fetched nonetheless.
A colleague confessed she often feigns non-recognition when she crosses paths with old friends because she does not want to dig up the past.
But I'm not afraid of my past, I protested. Neither was she, she said.
Sometimes it is only practical to do so. Some of us already have trouble touching base with the present, so why complicate matters by dredging up the past, she argued.
Perhaps she's right. We move on in life. Sometimes people who once mattered to us do not matter any more. They are now immaterial to our lives.
It sounds cruel -- categorising people as immaterial, but what do most of us do, if not compartmentalise things and people, to give our lives a semblance of order? We divide our friends into soul mates, mere friends and acquaintances.
And like it or not, Ah Fatt is now a stranger even though he was, once upon a time, a great playmate.
Yet, I couldn't help wondering why a simple smile seemed so beyond us...