The Rolling Stones' official itinerary for their Zip Code Tour lists only 15 shows, but at the rate they're going, they may end up playing twice that amount by the time they're finished.

Multiple sources in San Diego are reporting that the band played a secret show at the tiny 600-capacity Belly Up Tavern yesterday, several days after opening the tour at the city's Petco Park. According to Business Insider, the invitation-only gig was held at the behest of former HP chairman Ralph Whitworth, who's said to have paid upward of $2 million to have the band play for "400 to 500 friends."

A little extravagant? Sure, but Whitworth established precedent in 2003, when the San Diego Union-Tribune notes that he hired Paul McCartney to play a private show for his wife's 50th birthday. And as the same report adds, the Belly Up is the same place where Lady Gaga, Tony Bennett and the Foo Fighters played a private corporate event in January.

Employees at the Tavern reportedly signed a non-disclosure agreement and were unavailable to comment, but as you can see in the news footage above, there was definitely something happening at the venue during the afternoon of May 27, both at the service entrance — where gear reportedly belonging to the band was being loaded in — and in front, where fans were being shooed away by 1:30PM.

While there remains no official confirmation (or video) of the show, the city saw a flurry of social media activity around the gig, and has what purports to be the evening's 15-song set list.

The Belly Up performance comes shortly after the tour's first "secret" gig, which took place at the Fonda Theatre in Los Angeles and served as a warm-up for the Petco show. The next official stop on the Zip Code Tour comes May 30 in Columbus, Ohio, but where the Stones will actually play next is anyone's guess.

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