The sad thing is, I never even knew its name. My favourite bar, a place I go on about ad nauseam, and I never bothered to find out what it was called.
To us during that week in 2008, it was just "Tommy's bar", so-called because it was owned and staffed solely by a guy named Tommy. It had a proper Basque name as well, something formal that was slapped above the door, but I never bothered to learn it. It was Tommy's bar and that was it.
Let me tell you about Tommy. Tommy was Basque, but not traditional. First night I wandered into his bar, he was wearing skintight jeans and a Motorhead T-shirt with the sleeves cut off. Next night I walked in, he was wearing skintight jeans and a Motorhead T-shirt with the sleeves cut off. Third night ... you get the picture.
Despite his sartorial mastery, the crowning glory in the vision of Tommy was the cascading curls of his meticulous mullet, a long mane of rock-god glory that was trimmed at the top and sides but left to roam free at the back.
Tommy's bar was unlike any in San Sebastian. Where other places concentrated on good food and excellent wine and nice decor and music at a conversational level, Tommy's bar was dedicated to its owner's true love: '80s heavy metal.
There were no plates of snacks laid out on the bar like the other places because Tommy would probably tread on them during one of his not-infrequent climbs onto the counter to play air guitar. The place was dingy. The music was loud. The drink selection included beer or beer.
For an entire week a group of us - me, my partner, a bunch of Australian backpacker girls, a group of American students - patronised Tommy's bar every night. We drank the beers, we shredded imaginary fretboards and we had a ball.
Then we all left San Sebastian, and we never heard anything about Tommy and his bar again.
Every friend who has gone to Spain in the past four years has been told to visit Tommy's bar, the best place in the world (an opinion shaped, no doubt, by the giddy freedom of travel and the distortion of nostalgia), but all failed.
"Where is it?" they ask. I pause. I'm not sure. I could lead you there, but couldn't point it out on a map. It's down one of those small streets in the old town; it has a Jolly Roger flag over the entrance. It's near some other bars. Gah, I dunno.
"OK," they say. "What's it called, then?" Hmm. Even Google has failed me. It's as if it never existed; as if it were a hallucination, a dream bar that really was just that.
But now I'm back in San Sebastian. Different time, different friends. It's four years on, and the first thing I want to do when the sun goes down is find Tommy's bar. I'm aware of the dangers: it's a bad idea to try to recreate past travel experiences. You're dooming yourself to disappointment - it will never be as good as the original.
But I need to see Tommy. I have to go back to his bar, if for no other reason than to reassure myself that it was really there. We hit the old town for a night out, and the memories flood back. There's a bar on a corner just there - I'm sure this place used to do the world's best prawn skewers, so we duck inside to find out. I'm right. They did, and still do. It's a good start.
We head out the door and to the right. Twenty or 30 metres down the road, and it should be just here. This is where the Jolly Roger should be hanging; this is where Tommy and his bar should be.
I hold my breath as we take the last few steps, then spin and peer through the door.
It's gone. Tommy's gone. His bar is gone. It looks like the same shape inside, the basics are still there, but everything else has changed.
It's been modernised. There are pink neon lights on the walls. Flat-screen TVs play Rihanna music videos while young revellers sip expensive gin and tonics.
The hair metal is gone. The hair is gone. It's a cookie-cutter nightclub just as incongruous with its surroundings as Tommy's was, only for all the wrong reasons.
It's tacky, it's cheesy and it's very sad. We walk away. Time to find something new.
In retrospect, it probably would have been better never to have known, never to have found out the inevitable fate of the best bar in San Sebastian - maybe the best bar in the world. It should have remained a dream, a good memory.
But now I'm certain Tommy's bar is gone. And I never even knew its name.
Have you ever tried to return to a special place from your past travels only to find it irrevocably changed? Post a comment and share your stories below.