Reporter: When you're lost or stranded, sunrise is normally a welcome sight. But not in death valley. Not in july. Weather forecast for today mostly sunny high near 121. Reporter: Unprepared to... See More
Reporter: When you're lost or stranded, sunrise is normally a welcome sight. But not in death valley. Not in july. Weather forecast for today mostly sunny high near 121. Reporter: Unprepared to survive in the desert and possibly mislead by their gps donna, her daughter gina and nd jenny have driven aimlessly through 100 miles of wasteland. They measure their chances of survival now in droplets of water. There's only three ounces left. We are all dehydrated. Reporter: The gas is gone too last night their car had staggered to a stop. The car was empty. It was empty, empty, empty. Reporter: But with the punishing heat returning and the prospect of death, gina convinces her mom to try the car one more time. So got in the car, said a prayer, turned the key, and the car started right up. Right up. To this day, I cannot believe it. Reporter: Whether it had to do with condensation, the air temperature or maybe that prayer, the little grey hyundai is rolling again, but to where? How long? Back in florida daughter's daughter skye know something is wrong. Donna never came home and gina did not show up to work. Where is my wife. Where is my daughter? Where is jenny? Now it's like something is really wrong here. Reporter: They notify authorities in california and nevada. California highway patrol chopper pilots tyler johns and scott steel lift off from their base 200 miles south of death valley. Three and a half million acres, almost a thousand miles of back country roads. Our search area is daunting. Reporter: Still the searchers have one small clue given to them by donna's daughter sky back in florida. Running a check on donna's credit card accounts. She sees her mom made a purchase the day before. That t-shirt at scotty's castle. It's an unexpected break. But the inferno that is death valley is huge and unforgiving. But then, on the burning horizon the women seem to see a tiny patch of green. Recalling for them that strange note they found in the mailbox yesterday "we're under the big tree's" it said. Leg their car, riskihe exposure, they stagger two miles back from the road. It' not a mirage. There! Was a screened porch and three trailers. It was like. Reporter: This "paradise" has a curious collection of camping trailers, locked and abandoned during these hot months. And even a little dirty well water to share. Reporter: What did it taste like? Hot. Hose. It's hot hose. Reporter: But as night falls again they wonder if they have now only postponed the inevitable. I was, like, I don't want to die here. Nobody's ever going to find us. Reporter: As the third day begins even the searchers are growing doubtful. If we don't find them that day, we, we're pretty sure that they would be dead, and our next mission up to the park would be a body recovery. Reporter: For six hours the choppers sweep the skies. Though they are running low on fuel pilots johns and steel decide they will check one last remote corner of the park. Uh, saline valley, which is, in my experience, the most remote part of the park. Reporter: But tucked away in saline valley is that dusty camp with "big trees." We saw their vehicle next to a road, which we're like, hey, is that, is that a car, because we hadn't seen a car all day, it seemed like. It certainly looks like a vehicle. And I jumped out, put my sneakers on, grabbed the yellow emergency blanket, rushed out to the big tree. And there I see the chp helicopter. I waived that blanket. I heard her screaming and i just goes, donna, come out! I went running outside. Boy, I was so happy to see that. I cried. Got a phone call from the california highway patrol they've been found. Whew! Reporter: Recently "20/20" brought the women and the pilots together again. The reunion almost felt like being rescued all over. This is wonderful oh my god! Hello! How are you? I'm so happy to see you, you have no idea! Oh my gosh. Oh my gosh. I talk about you guys all the time. Oh, this is so nice. I like it. This is wonderful. Reporter: As for nell donna's old gps it was eventually given the boot. Seems it became stuck on only one direction. It just would not get off home. It just, home, home, home, home, home. Reporter: Suppose you can hardly blame it and anyway. Donna's bought a new one. Yes. Her name is rosy. She usually gets us back on the right track. And I know enough not to listen to every word she says. Continue 11 miles on california 190.
This transcript has been automatically generated and may not be 100% accurate.