A North Carolina mother says a phone tracking app saved her daughter's life in a car crash.

As the car carrying Catrina Cramer Alexander and her family navigated the dark two-lane road that snaked through the dense forests near Pilot Mountain in North Carolina, the mother's eyes were glued to her iPhone screen. It was late on June 7 and Alexander was searching for her daughter, Macy Smith, who had missed curfew and wasn't answering her phone. According to the locator app on Alexander's phone, the 17-year-old was nearby.

The small pulsating blue dot that marked Alexander's location kept moving closer and closer to where Smith was supposed to be, when suddenly, something caught her eye: a set of tire tracks running off the road.

"That's all I could see," Alexander told WFMY.

But the app, Apple's Find My Friends, wasn't wrong. Smith was there. Hidden from view, about 25 feet down the side of a tree-covered embankment, the teenager had been trapped in the wreckage of her car for almost seven hours - and she was alive.

"Having that location, if we didn't have that, we would have never known where to look," Alexander told WXII. "I'm certain that that is what saved her life."

Alexander and Smith could not be reached for comment late Sunday.

On the afternoon of June 7, Smith hopped into her white sedan and headed out to meet a friend, WXII reported. By the time she reached the winding road, it was raining heavily and the pavement was slick.

In a Facebook post shared the day after the crash, Smith wrote that her car started hydroplaning before careering off the road between two trees and flipping three times. When the vehicle finally came to a stop in the ravine, Smith said, she found herself in the back seat, her left arm pinned beneath the car and the ground.

"The first hour, I was frantic," she told WXII. "I was looking for ways to get out. I was thinking of just different things I could do."

She immediately started searching for her phone, her mind racing with questions. What if no one could find her? What if she didn't have phone service? What if the phone's GPS locator wasn't working? But the phone was nowhere to be found and the only thing within her reach was a Bible.

"The second I laid my hand on that Bible, I knew it was God telling me that it was all in his hands and it was happening for a reason, and that I would OK," she said.

So, Smith waited. She lay there and watched the sky grow darker, straining to hear anything that sounded like potential rescuers. One car drove by her without stopping, then two, then three. By nightfall, Smith told WXII, 28 cars had come and gone.

Then she heard the 29th car. Only this time, it stopped. The sound of doors opening and slamming shut were followed by what Smith had been waiting almost a half-day to hear - the voices of her stepfather and brother calling out to her.

"I knew they were going to show up and I'm so thankful for my family and we're such a tight family that I knew that I wasn't going to be there the whole night without them looking for me," Smith said.

Her family immediately knew something wasn't right when Smith was late coming home and calls or texts went unanswered, Alexander told WFMY.

"The lack of response was out of character for her," Alexander said.

Using the Find My Friends app, which allows people to share their locations with others, Alexander said, she pinpointed her daughter's whereabouts and set off to look for her. On Facebook, Smith wrote that her family found her around 10:30 p.m.

"My daughter is in a ditch, in a ravine," Alexander could be heard breathlessly saying in a recording of a 911 call published by WFMY.

For the entire time she was stuck alone, Smith told WXII, she never cried. But when her stepfather reached her and the pair held hands through the car's sunroof, the teenager said, her emotions overwhelmed her.

"I couldn't hold it in anymore because of the feeling of relief and knowing that I don't even deserve to be alive," she said. "It's unreal that I survived that crash."

In addition to fracturing her neck in the crash, Smith sustained nerve damage to her left arm, which was stuck underneath the car, writing that she "cannot feel it at all." Photos of the car showed a mangled white sedan missing its entire front windshield and several windows.

Alexander wrote on Facebook that what happened to her daughter was "a miracle."

"As parents, brothers, sisters, we can't really even articulate the feelings of gratefulness, of sheer awe, of overwhelming guilt, followed by extreme joy and, all the while, perspective . .. " she wrote in another post. "It's a roller coaster of emotions that just repeats itself that we can't even explain. That night . . . we won't ever forget, it's burned into our memories."

Alexander and Smith told WXII that the crash has shown them the importance of using mobile tracking apps and encouraged other families to do the same. Alexander said her family now uses the Life360 app, which has more features than Find My Friends, including crash detection, roadside assistance and a help alert that instantly sends a person's location to their emergency contacts.

"I know it's hard for teenagers to give up your privacy, but sneaking out and being places you don't want your parents to know about is not worth being trapped under a car for seven hours," Smith told ABC News.