I’ve been there, when my beloved first Canon EF was left behind in a car park many years ago. Unfortunately, there was little that could be done, except report it and hope for the best. These days, with a digital camera, there is another possibility: stolencamerafinder.
This is a free service (at the base level) for anyone who has lost a camera – or found one – and wants to do something about it. This article from the Sydney Morning Herald tells of its successes.