Oak Lawn police say two men drove a black Chevy Tahoe in front of a car driven by an 18-year-old man near 95th and Parkside.
The men got out wearing vests, belts with gadgets on them and possibly badges.
As the driver was giving the men his license, they grabbed his wallet and turned their backs to him.
They returned the wallet and told him he was free to go.
The driver later realized he was missing nearly $50.