I don't know who this dog belongs to, but I passed a couple of ladies on the bake path a few months ago walking two dogs, one who fit this description. The stopped me and asked if it was my dog. Evidently it had come over to play with their dog and they decided since they couldn't figure out who it belonged to, they just took it for a walk to see if they ran into the owner.
Apparently this pooch has a penchant for running away.