While trying to earn money at the country club, Bart acquires Denis Leary's cell phone after Leary angrily chucks it away. Bart keeps Denis Leary's phone and makes prank calls pretending to be Leary and when Marge finds out what Bart is doing she contacts Leary. Denis says Bart might as well keep the phone, but he advises her to activate the GPS system in the phone so she can track Bart's every move.
Principal Skinner and Agnes are driving across a freeway, only to run out of gas. Fortunately, a gas station is across the road; the downside is Skinner has to go across the freeway with a can of gas. With difficulty, he manages to get across the highway, but not before Milhouse manages to catch the whole hilarious scene on his phone. He calls a large variety of his friends to come see Skinner getting beat up by Barney, but doesn't call Bart. When Nelson asks why, Milhouse explains it's simply because Bart doesn't have a cell phone. At the Simpsons' home, Bart is taunted for missing out on laughing at Skinner. Bart decides to go to Marge and ask for a phone, though Marge explains she can't afford to get a phone for Bart; she also can't afford to fund a dream trip for Lisa to Machu Picchu.
Bart, deep in thought, takes a stride through Springfield. After passing the Springfield Golf Course, he is promptly hit by a golf ball. Angrily, he goes to hit it against the person who threw it at him; upon entering the course, it turns out Dr. Hibbert had accidentally hit him. Dr. Hibbert immediately pays Bart a dollar for retrieving the ball. Surprised, Bart takes the money, and decides to start a business: retrieving golf balls for money. Bart soon begins to make enough money to buy a cell phone. Upon learning of a celebrity golf tournament, Bart gets ready to retrieve the balls and finally buy a cell phone. However, his chances of earning that money are ruined when Groundskeeper Willie (or more appropriately, Greenskeeper Willie) takes the bucket of golf balls away from him with the intention of getting the payment that he felt Bart cheated him out of, causing Bart to sulk. Denis Leary prepares to go for a round (while being heckled by media personalities such as Krusty the Clown and Rainier Wolfcastle before he threatens to kick them out of show business if they don't stop), but misses when his cell phone rings at the same time. He angrily throws away his phone, which lands right beside Bart. Bart, gleeful he has a phone, quits his job and takes Leary's phone for himself. While going to inform Milhouse of his new cell, he receives a call from Brian Grazer, who asks if Leary would like to star in the film adaption of Everybody Poops. Bart, realizing the phone belongs to Leary, pretends to be him. Afterwards, Bart starts using Leary's phone to make prank calls to bars all over the world, order Viagra, (which he puts in Skinner's coffee), among other things. Marge overhears Bart and Milhouse's mischievousness, and finally confiscates Bart's phone. Leary recalls his cell, and Marge answers, apologizing for her son's behavior. Leary, still angry with Bart's tricks, suggests Marge activate the GPS in the phone, meaning she could track down Bart's every move.
Albeit guiltily, Marge activates the GPS system and returns the phone to Bart. Bart happily uses the phone, though it makes Marge guilty for spying on her son.
Using the GPS system, she is able to find where Bart is going: first she finds him goofing off in a construction site (which she correctly stated as a hard hat zone). Bart suddenly stops the forklift truck, causing Milhouse to get knocked out by a steel girder. She tells Bart off, then he takes an unconscious Milhouse home. Marge continuously tracks Bart with the GPS system: she grabs him from a rated R movie, gamboling at a horse race, and prevents him (just in time) from skating down steps and hurting himself. Lisa overhears Marge and Homer, and is shocked by the injustice. She immediately tells Bart, who is angry with Marge. Bart, thinking quickly, attaches the GPS chip onto the leg of a bird which sends his family on an national chase. While Homer, Marge, Lisa, and Maggie are searching for Bart, Lisa realizes that the bird is the one they'd been chasing. After checking research on her laptop, she discovers the bird is going to Machu Picchu, her dream trip they couldn't afford. She deliberatley lets the bird go free, so the family can chase it to Machu Picchu.
Meanwhile, Bart initially relishes his newfound freedom, but is horrified and frightened of being alone at night. Arriving in Machu Picchu in the morning, the family searches all over the Inca ruins for Bart. Marge, despite being exhausted, can't give up, but Lisa convinces her to rest on an ancient sculpture, below the statue of the god Viracocha. Marge quickly falls asleep. In her dream, Marge is whisked away by Viracocha, who shows her Ancient Peru. He teaches her how throughout history, parents who over-parented their children could never set them free. Upon waking, Marge learns that she cannot over-mother Bart, and must let him take steps for himself. Homer discovers that the family had been following a bird the whole time. Marge takes the family back to Springfield, where they find Bart and home. Bart says he didn't notice they were gone (for two weeks), so Marge, depressed, goes upstairs. However, upon reaching the stairs, she is stopped by Bart, who quickly begs her to never leave again. The episode ends with Lisa asking Homer where Maggie is; as it turns out, the family had left her in Machu Picchu, where she is being worshiped.
After the episode ends, a dedication to the memory of Paul Newman but instead of a picture a bottle of salad dressing with his face on it is shown.
IGN said, "This wasn't a terrible episode, but it just wasn't funny enough for such a serpentine storyline. Throw in a wasted Denis Leary, and you really start to think that 'Lost Verizon' could have been so much more". They gave the episode a final rating of 6.7/10. TV Verdict said, "it is a mostly solid episode, it feels like a missed opportunity for a show that garners more grumbles than acclaim these days".