We'll call our rock star "Frank", since that's only half his name, which will make him at least twice as difficult to identify.
Frank's kind of a big deal - just ask him. He says he's won two Grammys. He says he's got 5000 friends on Facebook. And tomorrow, he says, he's going to sign a three-album deal with Interscope Records.
It all seems too perfect: here I am trying to spend 24 hours living out a childhood fantasy of life as a rock star, and I've already met a real one. Well, so he says.
Still, whether Frank really is who he says he is is immaterial. This is Los Angeles. This is Sunset Boulevard "the Strip". It doesn't matter if you really are a star - if you truly believe you are, so will everyone else.
I meet Frank at a dive bar on the Strip one LA afternoon, while I'm drinking a beer and counting the hours until the Rainbow Bar and Grill opens, as I imagine most rock stars - or journalists posing as rock stars - must be doing. That's what Frank's doing, too, having a drink with a friend when we get chatting.
"Frank's kind of a big deal," his friend confirms, sipping a G&T.
I've only been in LA about four hours. Not so long ago, I was walking out of customs at LAX, being met by a suited man with my name on a placard. In LA, wannabe rock stars don't get cabs from the airport, they get "town cars". It's not quite a limo but, hey, I'm not quite a rock star.
My town car whisked me in tinted privacy to my accommodation: the ultra-cool Chateau Marmont. This is a hotel with rock'n'roll credentials. Led Zeppelin once rode motorbikes through the lobby. Anthony Kiedis wrote songs here. Lindsay Lohan lived here. John Belushi died here. Anyone who's anyone hangs out here. And for the next 24 hours, so do I. You know how sometimes you have a fantasy of what a place or an experience will be like and it doesn't measure up in real life? This is not one of those times.
My room at the Chateau is quaint, if a little shabby. You're paying for history here, not luxury. It has a window, however, that serves as a prime vantage point over the Chateau's courtyard, which is already starting to fill up with the LA lunch crowd: uber-cool men dressed in casual Armani, tarted-up actress types clutching ridiculous, celebrity-sized dogs.
Down at ground level, everyone seems to be looking out the corner of their eye, trying to spy someone famous. They look as disappointed with me as I am with them.
Over at a corner table, the contributing editor of US Vogue magazine, Andre Leon Talley, is picking at a sandwich. Excellent. I make a mental note to name-drop him in my story later.
But rock stars don't sit around at the Chateau all day, so I head out on to the Strip and that's where I meet Frank, with his trilby tipped at a rakish angle and his skinny white jeans artfully torn.
Together we head to the Rainbow Bar and Grill, a notorious Sunset hang-out for past-it music stars. The lead singer of '80s metal gods Motorhead, Lemmy Kilmister, still drinks here on a daily basis. The bar has had its day, really; but then, so has Lemmy.
"Lemmy here yet?" Frank asks the waitress as she seats us.
"Haven't seen him," she says. "He usually drinks out back, you might catch him there later on."
No wonder he doesn't drink in the main bar, it's filled with the likes of us: sightseers hoping to meet Lemmy. Disappointed, we down our beers and head back to the Chateau bar. More drinks. Dinner is for people who aren't rock stars.
Bar Marmont oozes class. It's dark, as if its clientele would prefer not to be recognised. Frank works the room. "You know, I've won two Grammys," I can hear him saying to a peroxide blonde at the bar.
"Really?" she says, impressed. Her eyebrows would be raising if they could. Frank decides it's time to move on again, this time to the rooftop bar at the W Hotel.
It's a hang-out for the rich and famous, Frank assures me. And he's friends with the DJ. Frank's kind of a big deal.
So Frank grabs his hat, grabs his girls and we're off. Turns out he really does know the DJ. I'm impressed. So impressed, in fact, that by the time the lights come on at 2am, I'm moved to utter those fateful, exciting words uttered by thousands of rock stars and wannabes before me: "Let's all head back to my room at the Chateau!"
Now that's living the dream.
A few days later I get a friend request from Frank on Facebook. I accept. And you know what? He really does have 5000 friends.