I am an aussie breeder and he looks like an australian shepherd he also looks like a mix of something else due to the ears sticking upright. Unless he is just doing that because you may have been calling his name. I would take him to the vet to see if he has a micro chip. If he does not then post flyers if no response you have a new dog.
Oh my goodness he is absolutely precious! Well, I hope the mystery is solved soon...about the owners and the breed. He was obviously loved and cared for by someone to be so sweet and well-behaved. In that case, they must be broken hearted, but dang I'd have pictures plastered all over town and ads posted in every paper and in every local vet's office if we lost our dog. But, if he doesn't belong to someone, I am glad he found you. :) Good luck! He's a real keeper!
We really did try to find the little guys home. When he ran up in our yard and started playing with the kids he was so skinny. He seemed a little scared. He almost smothers you when you give him hugs! I figured he had left home days before we found him due to how dirty and hungry he was. A week went buy and we were all in love with him. No response yet and signs are still posted!