There has been much discussion of how Charlie, Sam and Patrick failed to recognize the song playing on the radio while they drive through a tunnel as "Heroes" by David Bowie, and why it took them so long to track it down. In his original novel, writer/director Stephen Chbosky had the friends listening to "Landslide" by Fleetwood Mac. However Chbosky felt that song was unsuitable for the film, as he explained in an interview with Vanity Fair:
"Landslide" is a beautiful song, and I would have loved to include it, but it's a very soft ballad. The problem was when we got to the tunnel scene I just thought, We need something that's not soft. We need something that's driving, that's epic in nature, and "Heroes" was a perfect fit. Alexandra Patsavas, our music supervisor - it was her idea. Because I told her, "I know I've got a tall order for you, and I'm sorry, but I need I need an epic song that I didn't know in 1992." And she came up with "Heroes".
The film is set in the early 90s, before it was possible to search for song lyrics online. In those days, unknown songs could only be identified by trawling through record shops and asking people. Also, Bowie's original recording of "Heroes" was not a hit in the States, failing to make the Billboard Hot 100; the song finally charted in 1998 when the cover version by The Wallflowers was released. However, Chbosky has acknowledged and addressed the criticism of him selecting "Heroes" as an "unknown" song. Again from the Vanity Fair interview:
You and John Malkovich and Jim Powers [both producers on the film] could all gang up on me and say, "We don't believe it," and I will put my hand on a Bible and say, "In the early 90s, David Bowie was 'Let's Dance' to me. He was that guy." The whole 70s Bowie, because I was more into grunge, I came late to him. Listen, if you say to me, "The kids not knowing 'Heroes', it's not realistic," I will cop to it! Anyone who has a bone to pick, I can't argue. But I swear to god, it was real!
Also, remember that the events are set in Pittsburgh, PA which, while it had a thriving alternative rock music scene, was very much out of the mainstream glam rock that Bowie's music tended to be played frequently in. That is, kids living in Pittsburgh would have missed a great deal of the variety of music that those on major East Coast or West Coast cities would have been exposed to. Given the musical exposure and identity of that region at that time, it's actually much more likely that they would have been able to quickly identify the book's song ("Landslide"), than the movie's ("Heroes").