When three friends set off for a drive through the Australian outback last month, the few provisions they packed – beef noodles, biscuits and some cans of vodka – indicated they didn’t expect to be gone long.Then things went terribly awry.On Nov. 19, as the trio passed over a riverbed, their car got stuck.For three days, Tamra McBeath-Riley, 52, Claire Hockridge, 46, and Phu Tran, 40, tried to dig it out, surviving off what little they had with them in hopes they would soon be back on the road, the BBC reported. As their circumstances grew more dire and the car wouldn’t budge, they moved toward a nearby watering hole with McBeath-Riley’s dog, Raya.Fearing the worst as days passed and no one came to their rescue, they separated sometime around Thursday, hoping one of them would find help and guide rescuers to the others. Hockridge and Tran set out on foot together with a GPS and a compass. McBeath-Riley stayed back with Raya, close to the water she knew they needed to survive.She was rescued Sunday after Australian police deployed helicopters to search for the group. But Hockridge and Tran have not been found.McBeath-Riley told reporters outside a hospital where she was treated for dehydration Monday that when help arrived, she figured Hockridge and Tran were also safe. Now that she knows they’re still missing, “I’m worried to death,” she said.In the Australian outback, people and towns are few and far between, and Pauline Vicary, police superintendent for Australia’s Northern Territory, said the unforgiving region made the search especially complicated.“Because of the terrain that they have gone missing in, and because we don’t have a particularly focused area, we are still doing the helicopters,” she told the Australian Broadcasting Corp. “It’s quite a diverse terrain – there’s sandy dunes, there’s hard clay, there’s areas of dense trees but there is also rocks and ranges in the area as well.”McBeath-Riley told reporters the group initially survived by digging holes under their car to shelter from the sun. Once they reached the watering hole, they used a T-shirt to filter the unclean water, she said.Hikers and tourists have gone missing in this area before. In January, German tourist Monika Billen was found dead near Alice Springs after she disappeared while on a hike. Police also searched for her from the sky, using drones and a plane to try to spot her on the rugged terrain.Vicary told reporters Monday that police have identified one pair of footprints in their search for Hockridge and Tran. That could mean the pair, who McBeath-Riley said intended to walk together, unexpectedly split up.