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In a bizarre repeat of a high-profile incident last year, an Apple employee once again appears to have lost an unreleased iPhone in a bar, CNET has learned.

The errant iPhone, which went missing in San Francisco's Mission district in late July, sparked a scramble by Apple security to recover the device over the next few days, according to a source familiar with the investigation.

Last year, an iPhone 4 prototype was bought by a gadget blog that paid $5,000 in cash. This year's lost phone seems to have taken a more mundane path: it was taken from a Mexican restaurant and bar and may have been sold on Craigslist for $200. Still unclear are details about the device, what version of the iOS operating system it was running, and what it looks like.

While Apple has not publicly announced any plans for future phones, unconfirmed reports in the last few weeks suggest the launch date for the iPhone 5 is likely to be in early October. Other reports from Taiwan have set the date at September or October. (See CNET's iPhone 5 rumor roundup.)

Apple declined to comment after being contacted this morning. A spokesman for the San Francisco Police Department said the company did not file a police report based on the loss at the bar. Craigslist did not respond to requests for comment.

A day or two after the phone was lost at San Francisco's Cava 22, which describes itself as a "tequila lounge" that also serves lime-marinated shrimp ceviche, Apple representatives contacted San Francisco police, saying the device was priceless and the company was desperate to secure its safe return, the source said.

James Martin/CNET

Apple electronically traced the phone to a two-floor, single-family home in San Francisco's Bernal Heights neighborhood, according to the source.

When San Francisco police and Apple's investigators visited the house, they spoke with a man in his twenties who acknowledged being at Cava 22 on the night the device went missing. But he denied knowing anything about the phone. The man gave police permission to search the house, and they found nothing, the source said. Before leaving the house, the Apple employees offered the man money for the phone no questions asked, the source said, adding that the man continued to deny he had knowledge of the phone.

In an interview this afternoon, Jose Valle told CNET that neither the police nor Apple security ever contacted him. Valle, who owns the bar with his family, said however he does remember a man calling multiple times about a lost iPhone about a month ago. He told the man he would call him back if he ever found the phone.

"I guess I have to make my drinks a little less strong," Valle said.

After last year's embarrassing loss, Apple reportedly has taken extraordinary steps to protect its prototype devices from leaks. Next-generation iPhones are sent to carriers for testing "inside locked and sealed boxes so that the carriers can carry out checks on their network compatibility in their labs," according to the Guardian.

Apple developers have been given new iPhones with an upgraded processor -- the one that is used in the iPad 2 and is expected to appear in the next-generation iPhone. But the device "is virtually identical to the iPhone 4, and there is no way anyone can tell it's not an iPhone 4 based on the phone's exterior," a report at 9to5Mac.com says. Even last year's prototype was enclosed in a case designed to make it look like an iPhone 3GS.

Last year's prototype iPhone went missing when Robert Gray Powell, an Apple computer engineer who was 28 years old at the time, left it in a German beer garden in Redwood City, Calif.

In early August, San Mateo County prosecutors filed misdemeanor criminal charges against two men, Brian Hogan and Sage Wallower, for allegedly selling Powell's iPhone 4 prototype to Gawker Media's Gizmodo blog. An arraignment is scheduled for tomorrow.

Prosecutors obtained a warrant to search the home of Gizmodo editor Jason Chen, and indicated they might prosecute Gizmodo, but eventually decided not to file charges.

Under a California law dating back to 1872, any person who finds lost property and knows who the owner is likely to be--but "appropriates such property to his own use"--is guilty of theft. In addition, a second state law says any person who knowingly receives property that has been obtained illegally can be imprisoned for up to one year.

CNET's Josh Lowensohn and Elinor Mills contributed to this report