Several years ago a woman of my acquaintance who is a cat person came home to find a lovely Collie on her doorstep. She took her in, bathed her, fed her, got her shots and license because no one answered ads or flyers. Then after several months there was a knock at the door and a woman claimed the dog was hers. The dog did greet the woman but then moved away from her. The woman insisted she wanted the dog back and had some proof of ownership (I forget what). My friend was distraught. This Collie loved the cats and they had quite a happy household. My friend begged and offered to babysit the dog for a little longer. The woman allowed that but still refused to relinquish ownership. Sensing that there was a problem, my friend waited til an opportune moment and offered enough money when it seemed the dog's owner might need it. Sure enough, the Collie (Sarah was her new name) now has a forever home and the original owner relinquished ownership. Patience, however, was the key word here. This process took several months.
I hope for the sake of this found Berner that something can be worked out. An appeal to the best interest of the dog might be successful. Sue Sacramento