The thriller is not the thing. If we focused on the "mystery" of this film, then we would miss perhaps 80 percent of the film. I'm going to describe a scene, and it won't spoil the film, even though the scene is in the final quarter of the film.
Our protagonist is looking for his friend, Ron. He goes to a music venue where the Yardbirds are playing (and they are playing so well). There is static on Jeff Beck's speaker and he's really irritated at it, so he keeps hitting it with his guitar. Finally, he breaks his guitar on the speaker, throws the instrument down and smashes it with his foot. Then he takes the fretboard and throws it into the crowd who goes wild, trying to grab the broken piece of the guitar. Our protagonist doesn't care about the Yardbirds, but he goes after the fretboard and captures it, running out of the club. A couple fans run after him, hoping to capture the broken piece, but he outruns them. Finally, after the chase, he tosses the fretboard aside. Another man sees the debris, picks it up for a second and then tosses it back on the ground.
The film is about value. The broken piece of guitar has no value in and of itself, it is because it is associated with Jeff Beck and the Yardbirds that it has any value at all, and only to those who value the band. To a person on the street, it is a piece of garbage.
Great art, and an interesting character arc. I'd be interested to see the character a year from this time to see if this insight changed him at all.