A Minnesota waitress who says a customer told her she could keep a box containing $12,000 is suing after police impounded the cash as suspected drug money.

The wad of cash was left in a to-go box on a table at the Fryin' Pan restaurant in Moorehead, Minn., where Stacy Knutson works, The Associated Press reported.

Knutson said she followed the customer out to the parking lot to give back what she thought were leftovers, but the customer said, "No, I am good; you keep it," according to The Forum newspaper.

When she looked inside, she found three wads of bills -- $100s, $50s, $20s and $10s -- wrapped in rubber bands, her attorney, Craig Richie, told the AP.

Although she really needed the money, Knutson called police, who told her to wait 90 days in case someone claimed the money, The Forum reported.

No one did but police still refused to return the cash, saying it was being held in a drug investigation because it smelled of marijuana, Richie said.

Now, Knutson has filed a lawsuit in Clay County District Court, claiming the cash is rightfully hers.

Moorhead police Lt. Tory Jacobson told The Forum he couldn't discuss the matter, citing  an ongoing investigation "with suspicion of narcotics."