Déboussolé literally means 'disoriented' or 'bewildered', as if one has lost their compass. It's a more evocative word than simply 'confused'.
In the song, the narrator uses it to describe his feeling when the woman he's pursuing takes a long time to respond to his messages. He sings, "Ça m'a un peu déboussolé" (That left me a bit disoriented), highlighting his surprise and frustration at her unexpected lack of immediate interest, which throws him off his game.
This song is a hilarious look inside the mind of a guy whose ego just took a massive hit. Singuila kicks things off after a successful one-night stand, feeling pretty pleased with himself. He sends a follow-up text, which he cheekily calls an "office de SAV" [after-sales service], and considers it a done deal: "Agent dormant, dossier classé" [Sleeper agent, case closed]. He's confident, he's cool, he's in control. Or so he thinks.
Everything falls apart when she reads his message... and replies "longtemps après" [a long time later]. This completely throws him for a loop. His bruised pride comes out in the chorus, where he tries to flip the situation by insisting, "Non, elle n'a pas mon temps cette fille-là" [No, that girl doesn't have my time]. He tries to convince himself he's had better and doesn't care, but his obsession only grows. He starts checking her out again and decides he has to win her over, just to get his revenge. It's a funny and very honest story about how a little romantic rejection can make someone's ego go haywire.