You're right Phil. I'd do the same the thing, just contact the owner. My husband had his wallet stolen from his truck 4 years ago, and we never heard about it, until last spring. A woman called to say they had found some of his I.D. We picked it up, but there was no wallet. Then about 3 months later, we received another phone call, from a woman in a city, 3 hours from here. Her husband was a railway engineer, and he had to stop his train, while the maintenance crew worked on the rails. He was walking about, and he came across my husband's wallet, that still had all his cards in it for crossing the border. She mailed them to us, and I sent her some gift certificates for Tim Horton's to say thanks.
I'd do the same thing, and not go through the police.