The sand on Southern California beaches is periodically replenished by offshore or inland dredging operations (to keep the tourists happy). If you find nothing, that could easily indicate recent replenishing. You'll soon see you are not the only TH-er in the area--especially on warm days like we've currently experiencing.
A hint: Take a day to research where the crowd sits, then return either later in the day or early in the AM to that same spot. Hunt the paths to the beaches (the hillside at Carlsbad west of the 'free' parking lot at Carlsbad Village Drive). Hunt the areas in and around the sand volley ball courts--especially where personal effects are placed--or behind 'open' benches. Beyond all that, just enjoy the experience of out there swinging !!
Don.......