You lucky b#stard ! I just checked Carmel beach yesterday, and it was SO sterile that I walked around on the wet sand for 30 minutes, and NEVER GOT A SINGLE BEEP. Just utterly sanded in.
We do have a few "pocket cove" beaches here that have rules of their own. Ie.: don't depend on storms and swells and wind to erode. They just randomly go up or down a foot or two, with seemingly no connection to weather/storm/sea events. But they're not consistent.
I've heard of some beaches like you describe (typically inter-bay beaches, that don't have extreme sand movement) where you can silver at any time (not much different than hunting a land-site, since sand movement is minimal).
As far as the singular "scram", here's my thoughts on that :
http://metaldetectingforum.com/showthread.php?t=278842
I heard of a scram or two, on CA state beaches (very extremely rare), yet .... nothing ever became of them. Just someone having a bad hair day, or someone who you'll never bump into again, etc... Are you at liberty to say what entity/type beach yours is ? Eg.: city, county, state, or fed or .... ?