You could check your areas md clubs. Plus there's a site called lostmystuff.net. They notify other mders in areas of lost items. So they could find and return items. They contact you for specifics and you could meet. Object is to find items lost and return. That's the big reward anyways.
Hope posting about lostmystuff is against any rules, but that might help him find somebody close by if nobody here can assist. Plus the more people looking just might be better.
Good luck Iuck on finding the ring. If I could I would help.