David Heatherly’s sport utility vehicle got stuck in the snow on Sunday on a back road in the Lewis and Clark National Forest, where he had been taking photographs of the scenery and wildlife.

The 42-year-old postal employee had no phone signal and just a pouch of beef jerky, some water and coffee in his Chevrolet Trailblazer.

He said: “I’d seen stories of how people had basically been able to survive off that and I figured if they could do it, so could I.”

He napped for 45 minutes of every hour, then set his mobile phone alarm to wake him up for 15 minutes to turn on the heater, eat a small amount of beef jerky and listen to a Christian radio station, before going to sleep again.

Heatherly said: “Then I’d wake up and start it again. I played Angry Birds on the phone to stay lucid.”

His phone lasted thanks to his in-car charger, but Heatherly said the isolation became overwhelming at times and he found himself writing out his will in case he died trapped in the snow.

He added: “At one point, late Sunday night or Monday night, I wrote out a will just in case.

“Those moments passed. Not quickly, but they passed.”

The weather cleared on Wednesday, so Heatherly left his car and started walking and after six or seven miles, he emerged northwest of Augusta.

He came across the home of the Gibson Reservoir’s dam manager, who took him in and gave him a bowl of hot soup.

Rescuers had been searching for Heatherly across the rugged terrain around 80 miles north since his wife had reported him missing on Sunday night.