If it happened in California years ago and is not in the public record, did not result in charges, and did not result in an arrest, how do you think the officer got that information? Understand that it is not the case that every bit of information that some police department has obtained is available to every other law enforcement agency, especially in an entirely different state. You’d have to first figure out if, in fact, the person was told about it by this officer (contrary to your assertion, it may just be that he found it out by digging on his own rather than from the officer) and then, if it was the officer, how the officer found out about it. A lot of information is not actually protected by law, and if he obtained it from some source that is not protected he may have been able to freely share it with anyone. The details matter.