The teenager escaped when the three men left her alone for the first time in 29 days to get food, and she knocked on several doors before swimming across Thompson Lake to find help, Wyffels said.
A farmer who requested anonymity told WCCO he was on his way to work on Tuesday when he realized he forgot something and turned back, only to find Block standing in the grass at the back of his property.
Block, who had taken off her pants and shoes in the lake to make it easier for her to swim across, ran towards his car and asked him to call 911.
Block also helped police arrest Powers after she noticed his car driving past the home just as a deputy arrived, WCCO reported.
Police eventually tracked down the other two suspects after a state trooper spotted their car outside a home.
Block was reunited with her mother Sarah Block, who thanked supporters on a Facebook and posted a photograph of herself reunited with her daughter.
Barker tricked the 15-year-old on Aug. 8 by telling her he needed help with a family situation, Wyffels said.
When the two got to his house, his roommate Holby and friend Powers restrained her with zip ties and assaulted her.
Over the course of four weeks, the men transported her to several locations, including a cornfield and a foreclosed home in Grant County, Wyffels said.