Mommy, do you have your cell phone?" John-Paul May, 10, asked that question every time he and his mom, Sue, left home in Harrisville, Pa. On the waiting list since April 3 for a heart transplant at Children's Hospital of Pittsburgh, May knew his life depended on a call from the facility—and a quick response. But as mother and son spent the afternoon of May 5 listening to jazz at a nearby university, neither suspected that the important call was being made until state police Cpl. James Green appeared onstage and halted the concert. "Is there a Sue May here?" he called out. "The hospital found a heart for your little boy."

Sue May, 52, figures she didn't notice her phone ringing because she had set the device to vibrate so as not to disrupt the concert and then put the phone in her bag. Determined to make contact, staffers back at the hospital called her husband, Phillip, 58, at work and then the police. As dozens of officers fanned out across five counties, searching for the Mays in malls and movie theaters, experts used GPS to track Sue's phone to the concert hall of Slippery Rock University. "Everybody wanted to find this boy in the worst way," says Green, who helped get John-Paul to the hospital 45 minutes before their deadline. "We didn't want him to lose his chance at getting a heart."

Neither did Sue, knowing that her son's coronary artery disease (the result of chronic rejection of a heart he'd received at 10 months, after a failed repair of a hole in his own heart) could cause heart failure at any time. "I was relieved," she says. As she hurried him out of the auditorium toward a squad car, the crowd rose. "Everyone was clapping," she says, "and cheering."

Perhaps happiest of all is John-Paul, who is recovering well after the five-hour surgery. "He said, 'My guardian angel took care of me,'" recalls Sue. Adds Phillip: "Plus a couple of state troopers."

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