"But on the fourth day, Berg somehow veered off what he described as a poorly marked trail and ended up in a swamp."

"He fell, drenching his clothes, bag and food. His hiking boots fell off, but he was able to recover them. His phone, however, disappeared. 'It was like quicksand,' he said. Berg would spend the next 11 days frantically trying to find help, surviving on his small supply of freeze-dried food and drinking 'the most disgusting water that you could imagine.' Back home, his wife, Debbie, grew increasingly frightened as the days passed without word. 'Am I going to be a widow now?' she recalled thinking as her mind wandered to all the possible dangers on the island, including wolves and moose."

From "For 11 days, a lost hiker shouted for help. Then two kayakers appeared" (WaPo gift link).

The island was Isle Royale.

Berg — Craig Berg — was a 70-year-old man who thought that, with his phone and its mapping app, he was properly equipped. If you're trusting your phone for everything, it should not be possible for it to "disappear."

Read about Isle Royale, here, at Wikipedia, including its most well-known story of survival, that of Angelique Mott:

In 1845, an Ojibwe woman named Angelique and her voyageur husband Charlie Mott were left on Isle Royale, as hires for Cyrus Mendenhall and the Lake Superior Copper Company. They were hired and carried to Isle Royale by Mendenhall's schooner, the Algonquin, first to scout for copper. Angelique found a large mass of copper ore, upon which she and her husband were hired to stay and guard until a barge could come to retrieve it, promised in no more than 3 months' time. They were dropped off in July and were left stranded there until the following Spring. They were left with minimal provisions, which consisted of a half-barrel of flour, six pounds of butter, and some beans. A supply boat was promised to arrive after the first few weeks, but it was never sent out.... 

They lost their canoe in a fall storm, and their fishing net was destroyed. By January 1846, Charlie went mad with hunger and even threatened to murder and eat Angelique. He returned to himself, loving and soft, but was weakening greatly, and eventually succumbed to his starvation, dying. Angelique was forced to leave the body in the cabin and created a brush shelter for herself to live in. She survived by eating poplar bark, bitter berries, and by pulling out her own hair, plaiting the strands, and creating snares with it, by which she caught rabbits on rare occasions. In the Spring of 1846, the Algonquin returned, and brought Angelique back to her mother. 

She died in 1874, in Sault Ste. Marie, Ontario.

I note that he thought of murdering her to eat her, but she not only declined to eat him when he died of natural causes, she left his body to occupy the cabin and made a separate shelter for herself. It seems too much to believe — catching rabbits with nets snares made from her own hair.

ADDED: They made a movie about her: