I knew I left my wallet sitting on the back of may car when I drove away from my apartment. I retraced all of my steps walking along several roads where I drove. I couldn't find it. I moved to California without locating it, dreading having to get new ID and cards at a new address. After being in California for a week my brother calls me and tells me he just spoke to a police officer. Apparently they arrested a kid and my wallet was on him when they arrested him. Everything still in my wallet except around $10 in cash.
Your son's wallet could still turn up, good luck.