The Moscow Mule, a mix of ginger beer, lime juice and vodka, hit the Tampa Bay scene about two years ago in a shiny copper mug not long after it was named one of Oprah's favorite things. But as the cocktail has become more popular so have the mugs, worth about $20 each. Now a growing number of proprietors are forced to serve the concoction, which ranges from about $8 to $12, in glasses or ask customers for collateral in exchange for the drink.About $15,000 worth of copper mugs slipped out the doors of Datz in South Tampa over 17 months, according to owner Suzanne Perry. "We were all about having the correct presentation. We spent a good deal of money on real copper mugs," she said. "Unfortunately, they went missing at a rather fast pace. We 'lost' over a dozen a week."Now Datz serves the Moscow Mule only in a glass and doesn't even list it on its menu, though a photo of one once graced the cover."The cooler it is the faster it gets stolen," said Zack Gross, owner of Z-Grille in downtown St. Petersburg. He knew the copper mugs were getting lifted nationwide so when he got a dozen a few months ago he decided the restaurant would ask customers to hand over their driver's licenses as a deposit of sorts to be returned when the cup comes back."We've had pretty good success with that so far. We did have one swiped that no one noticed. Another guy we caught on camera stealing one," he said. The Moscow Mule, which was supposedly invented in the United States in the 1940s but took the name Moscow because of the vodka, is the third-best selling cocktail at the Renaissance Vinoy Resort. It's behind the Mojito and Bloody Mary. The hotel has sold 450 of them — in a glass — in the past three months.The Vinoy made the switch from copper last year after a few dozen cups "found their way out the door," according to beverage and food manager Alex Bolstridge."But you can tell from our sales (the switch to glass) hasn't impacted its popularity," she said. "The copper is a cute look. It's supposed to keep the items fresher and cooler and bring out the freshness of the lime."Since the Vinoy uses all fresh ingredients and they can be seen better in a clear glass, Bolstridge believes customers enjoy it just as much that way.Tampa's Ocean Prime offers a different twist on the drink, using rum instead of vodka. They call it a Caribbean Mule. "Because we started with a different version we didn't ever use the copper mugs," said Jo Truett, who works at the restaurant. "I have friends in the business and they tell me they are definitely having a hard time keeping them in the building."The Sheraton Sand Key serves Moscow Mules in glass as well. Bartender George Pietrowski said it's a very popular drink, but once in a while customers cancel their order when they learn it won't arrive in a frosty copper mug.Establishments look at the same problem and its solutions differently. Perry at Datz said she considered asking for driver's licenses but thought it seemed rude to imply somebody might steal simply because they ordered a drink. Gross said his staff apologize to customers for having to take a deposit on the mugs and they seem to understand. "It's not just a problem with Moscow Mules, people steal anything, even Splenda," Gross said, adding that he probably loses 25 sets of silverware over the course of a year. Contact Katherine Snow Smith at [email protected] Follow @snowsmith.