found a digital camera.

[Melalvai]

I don't know the answer but we found a camera and put up a sign just like you did, only maybe not so big, and less than a day later the person called. That was a few years ago and digital cameras were a little pricier than they are now. Good luck returning to the rightful owner.

[malkin]

Give the owner a week or so.

[Biciclista]

I have heard of cameras being reunited with their owners by LOOKING at the photos..
You might see where they live, who they are, where they eat.