The man was discovered disoriented and in shock on a regional road southeast of the French city by a woman shortly after 5am on Saturday, Le Dauphiné Libéré reported online.
He had flagged down the motorist for help between La Verpillière and Satolas-et-Bonce, south of the Lyon airport, according to the report.
The woman sought help after the man, who spoke only English, kept repeating the term “kidnapping”.
The international relations student from Philadelphia is working as an intern for the United Nations in Geneva, the newspaper said.
Interviewed by police from the town of La Verpillière, the victim explained that he had spent part of Friday evening at the Zoo, a discotheque in downtown Geneva, according to the report from Le Dauphiné Libéré.
Upon exiting the club late at night, people he had met at the disco, including a young woman, offered to take him home, he told police.
But the situation quickly turned ugly.
One of the occupants of the car blindfolded the American and warned him not to struggle.
He was then hit multiple times on the thigh and driven to the outskirts of Lyon.
The American told police he was robbed of all his valuables, including two mobile phones, his bank cards and US passport.
He was abandoned in the cold where he was ultimately able to flag down help.
An investigation was launched in cooperation with Geneva police, who discovered that the American man had left his jacket in the Zoo club, suggesting that he was enebriated when left, Le Dauphiné Libéré said.
However, one of his bank cards was taken by the thieves and used three times, including once at a Marseille petrol station, when it was last used.
The investigation continues.