"Then, I asked her, 'Do I get one too?'" Nathan recalled. "Part of me was out there doing that."
The light moment signaled the completion of an incredible journey for Rauh, now a senior at Lutheran South and winner of the school's 2019 St. Louis Post-Dispatch Scholar Athlete award.
Madeline grabbed her first state medal with a transplanted kidney in her body, one donated by Nathan a few years earlier. She said it was the best moment of her young life.
"It made me look back on things and feel proud of how far everything had come along," Madeline said. "And how he helped me get to that point."
Less than two years earlier, Madeline wasn't sure she'd ever be able to swim at a state-caliber level. Diagnosed with a failing kidney months before her freshman year, she spent an entire year waiting and hoping that a donor could be found.
Madeline was forced to go though her first year of high school spending night-after-night hooked up to a dialysis machine to keep her body functioning as normal as possible.
Her entire freshman campaign was a day-to-battle with little or no energy in her body.
"A lot of nights I just had to stay home," she said. "I couldn't go out. I was limited physically."
Explained her best friend and fellow South senior swimmer Isabell Banks, "She was so sick and I felt so sorry for her. But she never complained. She made the best of it."
All that suffering changed — thanks to Nathan, who still remembers his reaction when he found out that he was a suitable donor.
"So happy," he noted. "Then it was, 'How quick can we get this scheduled?'"
In mid-June of 2016, the two underwent simultaneous surgeries at St. Louis Children's Hospital and Barnes Jewish Hospital with mother Julie by their sides.
The operations were a rousing success.
"You can't describe a feeling when you know everything is going to work out," Nathan said.
Actually, the post-surgery recovery was tougher on Nathan, who needed almost six months to return to normal.
"Leading up to it, all she had to go through, it was more difficult on her," Nathan said. "Then after the surgery, it was harder on me."
Which is normal with kidney transplant patients.
What was not normal was Madeline's quick recovery time. She went right to the water after clearance from her doctor and immediately shaved eight stokes off her times in the butterfly and 200 individual medley, her two signature events.
That rapid progression eventually led to the sixth-place finish at state, which Madeline duplicated in February on a return trip to state as a senior.
"She'll go down as one of the best swimmers we've ever had here," Lutheran South athletics director Mark Linneman said.
Rauh went on to a stellar performance at the Transplant Games of America in Salt Lake City following her junior year. She won gold in the 50 butterfly and 50 backstroke and also grabbed five other medals at the national competition, which is held every two years and features athletes that have undergone major transplants.
But Rauh does not necessarily want to be known for her swimming skills. Or as the girl with a new kidney.
Her passion is art and animation.
She has already been accepted to the prestigious Savannah College of Art and Design in Savannah, Georgia.
"I love transforming what's in my head into something aesthetically engaging," Rauh said. "The storytelling that comes with what you create — it's a great way to connect with people and make a statement."
A 4.0 student ranked 11th in her graduating class of 119, Rauh's art can be found all along the hallways at South. She said her best work came out of a series of self-portraits with herself as some of major characters in the Kill Bill movie series. Banks loves Rauh's recent rendering of music icon David Bowie.
"She has such a natural ability," said Danielle Jahnke, the head of the Art Department at Lutheran South. "Her color sense is amazing. If she wants to do anything art related — she's going to find a way."
Rauh, who is also a cheerleader at South for the football games, has done volunteer work at Children's Hospital and with the Christian Friends of New Americans.
Plus, she has the ideal summer job — working at the iconic Ted Drewes Frozen Custard stands.
There were times when Rauh struggled to find the words to thank her father for the incredible gift.
But Nathan said it's not words, but her actions, that give him the most joy.