The previous Sunday, he'd taken a call from an assistant athletic director at Arizona State, who'd pitched the idea of Bowman taking over the university's struggling swimming program. Bowman was going to be in Mesa, anyway, to coach Phelps and others in an Arena Pro Swim Series meet, so he agreed to a courtesy meeting. But with his focus firmly on preparing for the 2016 Olympics, he considered the possibility "very far away."
Less than two weeks later, he was back in Tempe wearing a maroon and gold tie, being introduced as the Sun Devils' next coach. Phelps said he would follow his coach from Baltimore to Arizona.
The story of Bowman's startling move is one of a university making a convincing case but also of a coach embracing his own restless spirit.
"I just don't think I can be in one place my entire career and stay there," he said in an interview last week.
Bowman had already concluded he would step down as head coach of the North Baltimore Aquatic Club after the 2016 Olympics in Rio de Janeiro. He'd led the club since 2008, when he and Phelps returned to Baltimore in glory after the swimmer claimed a record eight gold medals in Beijing. Seven years in, he was growing tired of the administrative side of the job.
Bowman sensed he would need a new challenge after next year in what he termed "the post-Michael era."
Arizona State simply accelerated the clock, promising substantial resources and a commitment to building one of the best swimming programs in the country. Bowman had enjoyed coaching Michigan from 2005 to 2008 and he left that job with a sense he had more to do in college swimming. He particularly liked the idea of revamping an underachieving program (Arizona State even briefly dropped men's swimming in 2008).
"I kind of like the idea of building something," he said.
But he needed to ask Phelps before he could take the plunge. Theirs is a relationship that goes well beyond the usual athlete-coach bond. Bowman has guided Phelps since he was 11 years old and in recent years, they've morphed into friends and business partners.
"As long as he's swimming, I'm going to coach him," Bowman said. "He's done so much for me, and that's my commitment to him."
So if Phelps had nixed a move to Arizona, Bowman would have remained in Baltimore. Instead, Phelps responded enthusiastically.
"His reaction was, 'Yeah, let's do it,'" Bowman recalled. "He's very smart about swimming and that whole world, so I also had the sense that if he thought it was a good idea, that was probably a sign it really was a good idea."
Phelps said he felt no hesitation. "I'm not going to swim for anybody else," he said last week after teaching a water safety lesson to children from the Boys & Girls Clubs of Metropolitan Baltimore, part of his foundation's #imsafe initiative.
Phelps gently coaxed the pack of grade schoolers through laps in the pool at Meadowbrook Aquatic Center, a familiar setting he'll soon leave. He seemed upbeat as he talked about searching for a house near a golf course in Arizona and working on a year-round tan in the desert climate. He's viewing the move as the kind of temporary one many adult professionals make for their jobs.
"I didn't know what [Bob] was going to do," he said. "I know after I'm retired again, he is still very excited about coaching. We can see it here. And he wants a change. He wants to get back into the college atmosphere. He said it to me and I was like, 'You know, if that's what you want, I'll follow.'"
Other top NBAC swimmers, including 2012 Olympic gold medalist Allison Schmitt and 2013 World Championships silver medalist Chase Kalisz, will also move to Arizona, where Bowman will start work in August.
Phelps felt out of sorts when he and Bowman first went to Michigan in 2005, but he was still a kid in many ways. He's now about to turn 30 — engaged to longtime love Nicole Johnson and working on a sober life after he was arrested for drunken driving last year.
"I think we were both kind of looking to shake things up a little bit," Bowman said. "He sees it as a fresh start, and I do too in many ways."
Bowman, 51, believes the move will allow him to simplify his life. Others at the university will help with funding and logistics, so he'll have more time to think pure swimming. He figures he has at least 10 good years left in coaching.
His most immediate and scrutinized task will be fine tuning Phelps for a fifth Olympics. Bowman says his star pupil continues to train harder than he has since 2008, banging out nine or 10 workouts a week. He never did more than six in the run-up to the 2012 Olympics or during his comeback to competition last year.
But the grind has not produced stellar results in Phelps' first two meets since he returned from a six-month suspension for his DUI arrest. He particularly struggled at the May 14-17 Arena Pro meet in Charlotte, N.C., where he failed to qualify for evening "A" finals in three of five events.
A frustrated Phelps said his legs felt disconnected from his upper body. "When I see people tearing away from me off the wall, I know something's not right," he said to NBC commentators after his last race.
"He didn't look good," said NBC swimming analyst and former Olympic gold medalist Rowdy Gaines. "He was pissed, and it was the first time I haven't heard him find a silver lining. … But there have been times before, five or 10 years ago, when he didn't look good. And he always came back from it."
Bowman said he's unconcerned, noting Phelps' body is no longer used to the workload he's undertaken in recent months. He's swimming slower than he did last year in part because he's actually tired from workouts. But Bowman has faith, based on nearly two decades of observing Phelps, that the work will pay dividends when the biggest meets roll around.
"I think it's surface frustration," Bowman said. "We both feel like he's doing the right things and just not seeing the fruits of it yet."
Phelps still hates to lose, regardless of the the setting or the broader explanation. "I guess it's a learning experience, and it's good that it happened there and not at a bigger meet," he said last week. "The frustration that I'm having now, it's I'm not 17 anymore and I can't just bounce back from the work that I'm doing."
Phelps will swim again June 18-21 at the Arena Pro meet in Santa Clara, Calif. But he'll look to make his big splash for the year at Phillips 66 Nationals in early August. Bowman said that meet, in San Antonio, Texas, will be an important step for Phelps as he tries to build confidence entering final preparations for Olympic Trials and the 2016 Games in Rio.
"Even if you're Michael Phelps, you can't endure having your brains beat out forever," Bowman said.
Asked if he needs a more satisfying meet in the near future, Phelps responded with a self-deprecating laugh. "It would be a confidence booster," he said. "It would show me that what we're doing is actually working. I mean, do I know the stuff we're doing is beneficial? Yeah. I've gone through it for a long time. Some of the stuff that I'm doing I know will pay off. It's just a matter of time. But it is frustrating at meets just getting destroyed every time."