I found a dog I didn't recognize so I looked for its owner.
Why did you want to find the dog's owner?
I wanted to return the dog to its owner.
It is good to try to find the owner of a lost dog. So you should ask around and about a stray dog's owner.
It wasn't a stray dog. I just wanted to find out where the dog lived.
I hope you've been able to find the dog's owner; that is a very nice thing of you to do. If you're still having trouble and you know the dog's not a stray you could take it to the vet and see if it's got a microchip.