The strange tale of an alleged iPhone 5 prototype that went missing from a lively San Francisco tequila bar in July grew even stranger Friday with the disclosure that Apple (AAPL) security personnel teamed up with San Francisco police officers to search a Bernal Heights home for the device, but that the police officers were not the ones who went inside.

The iPhone, which reportedly disappeared from Cava 22 in the Mission district, had been traced electronically by Apple to a single-family home, according to a news release Friday from the San Francisco Police Department. The SFPD did not identify the occupants of the home, but the SF Weekly reported that Bernal Heights resident Sergio Calderón said his home was searched for the missing phone by people who claimed to be San Francisco police officers.

After first telling this newspaper that it could find no record of its officers taking part in the search, SFPD on Friday acknowledged its personnel had gone to the house, but said only Apple employees went inside to search.

“Apple employees called Mission police station directly, wanting assistance in tracking down a lost item,” the SFPD said in its news release. “Apple had tracked the lost item to a house in the 500 block of Anderson Street. Four SFPD officers accompanied Apple employees to the Anderson street home. The two Apple employees met with the resident and then went into the house to look for the lost item. The Apple employees did not find the lost item and left the house.”

Apple on Friday declined to comment. But the episode is mushrooming quickly into a huge embarrassment for the Cupertino tech giant. The notoriously secretive company was stung last year by a similar incident when an iPhone 4 prototype was left inadvertently by an Apple engineer at a Redwood City beer garden. It was later obtained by the gadget website Gizmodo, then disassembled and deconstructed online in photographs and text for all the world to see — a bit sooner than the September 2010 date Apple had been planning to let the world see it.

Apple has yet to announce a release date for the next iPhone, though analysts expect it could come as early as this month.

The latest case of an apparently missing iPhone is even weirder and potentially more serious. If it turns out that Apple security personnel entered Calderón’s house posing as police officers, the company could be dealing with a bigger PR mess than simply the premature unveiling of one of the hottest products in its pipeline. Impersonating an officer is a crime.

A woman who answered the phone at Calderon’s home Friday evening said he was not home and hung up.

Earlier Friday, SF Weekly reported that the Apple security personnel “scoured Calderón’s home, car, and computer files for any trace of the lost iPhone 5. The phone was not found, and Calderón denies that he ever possessed it.”

SF Weekly went on to say that in an interview Thursday night “Calderón told us that six badge-wearing visitors came into his home in July to inquire about the phone. Calderón said none of them acknowledged being employed by Apple, and one of them offered him $300, and a promise that the owner of the phone would not press charges, if he would return the device.”

The article quoted Calderón as saying, “When they came to my house, they said they were SFPD. I thought they were SFPD. That’s why I let them in.” Calderón told the paper that he only agreed to the search because he assumed the two people conducting it were police officers.

Calderón also told the paper that the people he let inside his house asked threatening questions about him and his family, including references to his immigration status. “One of the officers is like, ‘Is everyone in this house an American citizen?’ ” Calderón is quoted as saying in the SF Weekly article. “They said we were all going to get into trouble.”

In the SF Weekly article, Dangerfield stressed the seriousness of Calderón’s allegations. “This is something that’s going to need to be investigated now,” he told the paper. “If this guy is saying that the people said they were SFPD, that’s a big deal.”

SF Weekly said one of the men left a phone number with Calderón, which the paper traced to Anthony Colon. According to a public profile on the website LinkedIn, Colon, a former San Jose police sergeant, is employed as a “senior investigator” at Apple.

Contact Patrick May at 408-920-5689. Follow him at Twitter.com/patmaymerc.