CNET:

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.

Your Mac Life’s Shawn King and I were discussing this story this afternoon. It’s interesting to note that the San Francisco Police said no police report was filed, yet a police officer accompanied Apple investigators to the house.

Seems clear to me the source is the cop that was on the scene with Apple.