Such exchanges are the reason Hackett traveled 8,000 miles from Australia to Arizona last month to stay with Phelps and his wife, Nicole. It wasn’t his first visit. He has used their home as something of a halfway house, joking that he spends so much time with them that he is getting mail there.
His life in Australia, where distance swimmers can become celebrities on a par with N.F.L. quarterbacks in the United States, started careening out of control several years ago. In February, it derailed in a very public fashion.
He visited his parents’ Gold Coast home, and his father, Neville, called the police to report that Hackett had been drinking and had suffered a mental breakdown that sent him into a rage. The Olympian was taken to a detention center in handcuffs — a scene that was broadcast across Australia and set off a social media frenzy.
He was released without being charged, but his family was unable to find him the next morning. Alarmed, Neville Hackett stepped before television cameras, described his son as a missing person in urgent need of help, and implored him to come home. “Grant, let us know where you are,” he said. “We love you and we want to help you.”
Phelps followed the drama from Paris, where he and Nicole spent Valentine’s Day. He learned about what was happening in Australia through a text message from Allison Schmitt, another Olympic swimmer.
Phelps, who considers Hackett one of his dearest friends, sent a flurry of texts to him and then paced in his hotel room while he waited to hear back. Nicole Phelps recalled her husband saying several times, with increasing urgency, “We have to convince him to come home with us.”
Hackett soon contacted his family, saying he was safe and simply hiding from the humiliation. Phelps could empathize with Hackett in a way few others could. Along with his 28 Olympic medals, Phelps accrued two arrests for driving under the influence — the second one after the police stopped him for going almost twice the speed limit on a road in Baltimore, his hometown. He had also been photographed holding a bong at a private party, an image that ended up in a British tabloid.