Give that mailman a kiss
I bet the guy that has him has a story too. Oh you know, I just found her, didn't know, someone gave her to me....yada, yada, yada. Guess it doesn't matter long as she gets home

I found a chocolate lab puppy once, kept her overnight, the next day there were literally hundreds of flyers out for her. I'd have had to said I was blind to miss them.
Thought of something else.....ever see a lost dog's reaction when their owners show up? While that lab puppy was friendly and kissy to us....she went nuts when her owner showed up. They wouldn't have even needed proof she belonged them (or them to her)....it was obvious