At a minimum, they owe you for the three weeks that you worked. You should return to the store to speak to the manager directly. If they ask you to leave the premises, do so immediately without fuss or comment. Thereafter, send a letter to HR about the situation. If you don't hear anything from HR, at the least, you can sue the store for your wages and report them to the Department of Labor for labor violations.
Also licensed and practicing in New York.
