I would check out lost dog sources in your area. I see you're not in the U.S. and so don't know how it is where you live. Here, there are shelters that have lost dog lines. I connected with an owner through one of those for a dog I found once.
However, I would not post photos on posters or online or a complete description anywhere. That makes it all too easy for someone who is NOT the owner to claim the dog is his and walk off with him, and someone who does that is not likely to have good intentions. Post something general but hold back some particular bits of information such as about that oversized collar, the sex of the dog, etc., so that you can weed out any fakes like that.
However, I would not post photos on posters or online or a complete description anywhere. That makes it all too easy for someone who is NOT the owner to claim the dog is his and walk off with him, and someone who does that is not likely to have good intentions. Post something general but hold back some particular bits of information such as about that oversized collar, the sex of the dog, etc., so that you can weed out any fakes like that.
