Investigators said two men drove Fannie Miller, 12, and her sister, Delila, 6, to a house about 30 miles away near Richville, N.Y. The men told the girls to stay at the house and left.
The sisters walked to a nearby house, where they got help and the police were notified, officials told WWNY-TV.
Fannie and Delila disappeared Wednesday at about 7:30 p.m. from the family stand in Oswegatchie, N.Y., on the St. Lawrence River. The St. Lawrence County sheriff issued an Amber Alert early Thursday and authorities began a massive search.
The search was complicated by the family's religious beliefs. The Amish, a traditionalist Protestant group founded in the late 17th century, avoid modern technology, including photography.
A police sketch artist created a portrait of Fannnie based on conversations with her family.
District Attorney Mary Rain said the girls were "cold and wet" but otherwise unharmed when they turned up.