A Utah woman's story of survival after spending 11 hours in freezing temperatures in a rural Utah canyon paralyzed by two broken legs is a precautionary tale in wilderness survival, medical experts say.

Kellee Healy of Emery County, Utah, fell 50 feet down a rocky canyon while hiking in the rural Ticaboo Canyon area  near Lake Powell, along the Utah-Arizona border. She had traveled there Dec. 21 with her husband, Todd Healy, in celebration of her birthday, the previous day.

When the couple arrived at the canyon, they decided to split up and hike their own paths on the trail, a critical mistake, medical and disaster experts say. "They never should have split up," Dr. Richard Bradley, chief of EMS and disaster medicine at the University of Texas Health Science Center in Houston, told ABCNews.com.

"Always have a buddy with you when you're hiking out away from civilization," he said.  "They're very lucky to be alive."

Lucky is anything but what Todd Healy considered himself to be when he returned to the spot where he and his wife had parted four hours earlier, only to discover her lying at the bottom of a canyon, 200 feet below, covered in blood, with her bones protruding from her legs.

"I looked over there and I could see that she was not moving," he told local ABC affiliate ABC-4 this week in the couple's only interview since the ordeal.   "My first thought was that she was dead."

Kellee Healy was not dead, but severely injured, the full extent of which would not be known until 11 hours later, when she was finally reached by an AirMed helicopter tracked down by Todd.

With no cell phone coverage in the rural park to reach authorities, Todd immediately began performing first aid on his wife, building a fire and lying behind her to keep her warm. "Given where they were and that he was not able to go out and call 911, that was the right thing to do," Dr. Bradley said of Todd's first-responder actions.  "There was no way he was going to get her out."

With his wife by the fire, Todd went into even quicker action, realizing his window of daylight in which to get help was now less than two hours.

It took 30 minutes for Todd to hike out to the couple's parked car, and another 20 minutes to drive into cellphone range before he was finally able to reach a 911 operator and give the trail's GPS coordinates for help, according to the timeline of events he provided to ABC-4.

The decision by Todd to search for help on his own, and leave his wife behind, was another one crucial to his wife's survival, according to Dr. Billy Goldberg, assistant professor of emergency medicine at Bellevue Hospital Center and the NYU Langone Medical Center in New York City.

"You're not supposed to move somebody because, in a lot of cases, you can make injuries worst,"  Goldberg told ABCNews.com.  "It's hard to imagine how he could have gotten her out in the condition she was in."

While her husband searched for help, Kellee Healy lay back at the canyon site wearing only thermals, jeans and a sweater, as the temperature dipped down to a near-freezing 35 degrees.

"One of the things we say is that 'Cotton Kills,'" Dr. Bradley said of a common wilderness mistake Kellee unintentionally made in her clothing choice.

"People think that blue jeans and sweatshirts protect them but, if something unexpected like this happens, cotton does not protect from cold weather," he said.  "I'm very surprised that she survived the night."

Confident that help was on the way, Todd returned to his wife's side in the canyon, only to find that he had been too optimistic.

The couple was forced to wait another five hours huddled together while emergency officials were delayed by strong wind and snow in the surrounding area. "I would lay behind her and warm her and rub her and rub her all over," he said.

Finally, 11 hours after Kellee's fall into the canyon, an Air Med helicopter landed at the couple's site and pulled her to safety. "It was just like an angel being sent from heaven," Todd said of seeing his wife whisked away.

It was only once Kellee received medical treatment that the extent of her injuries became clear.

She suffered a fractured skull, pelvis, hand, sternum, ribs and shoulder blade.  She also lost her toes, likely due to frostbite, and will have to undergo months of physical therapy to regain her strength.

"Their story makes you think about the importance of being prepared for the unexpected," Dr. Bradley said.  "One of the things that's important if you're hiking away from civilization is that you have a plan of where you're going to go, and that you leave that plan with a person who's not going with you."