Yeah you're right Mark. That would be the exception. This was a high-end ritzy tourist town, with a well-staffed police dept, that does nothing but cater to the jet-set golfer crowd who lives here (mostly vacation homes at the beach-side enclave). And they weren't even necessarily trolling to find "violaters" in my case either. It was just a coincidence, and apparently when lady cop saw the term " ... metal detector ..." the wheels in her head must've started turning.
The email back to me was along this lines:
"You might also find other valuables on the beach with your metal detector. Therefore in the future, we would appreciate it if you would stop at the dept, on your way out of town, and drop them in the night slot, so as to be in compliance with the law. Because our dept. receives lost jewelry reports from time to time".
At first I thought "what the heck is she talking about ... "... to be in compliance with the law ..." Until I started sleuthing CA lost & found laws, and saw what she is talking about. Oooops. Then it only made me wonder "gee, if this is against the laws for persons to make their own attempts to re-unite things over a certain value [that they are to be turned over the police, not your own methods], then ........ what's to stop a district attorney from merely trolling craigslist, see what items appear to be over XX value, and presto, start prosecuting people?".
I mean, heck, you can look at ANY craigslist, in ANY city in the USA, and always see items there for the "found" section. Ie.: found mountain bike, or found ring, or found ......... .whatever. Right? But no, your right, it's probably more akin to a "blue law", that's simply meant for actual usage/implementation when in cases of a Brinks armored car door opening up on the freeway, or your neighbors cow wanders into your yard, etc...