We had some thefts from boats at our club last year. It caused some hassle, but we ultimately got our gear back and the thief was successfully prosecuted. Although the loss of a few shackles isn't the end of the world, if bigger items are taken, don't give up: We lost a trampoline from a Hurricane 5.9, a mainsheet block (left for just the one night!), and jib blocks from a Nacra 6.0, as well as other sundry items. If this happens to you, look back at recent sales of relevant boats on eBay, etc. We found a likely candidate, traced the name and general location of the buyer, and confirmed this with the eBay vendor. The electoral role gave us some addresses to check out, and long story short we found the boat, complete with stolen parts. The police were very interested (and had unofficially provided another address we might want to drive by in our search for the boat, based on the evidence above). Hopefully the word has gone out that it's not worth stealing specialist equipment from a close-knit community.