One morning last month, Woodacre resident Tim Cain started his 2009 Toyota Prius, and what he heard sounded more like a Harley Davidson motorcycle. A loud revving noise was coming from under the passenger’s seat, so he laid on the ground and found a large cavity that wasn’t supposed to be there. His catalytic converter was stolen—one of more than 350 thefts in Marin this year. A couple hours later, he was in his garden…