Have to agree with Ditch your rites to the pup were lost once you handed the papers over to the first owner who then signed the dog over to the local rescue centre and are now the rightful owners
You could you attempt to get someone else to rehome/adopt the dog ..Most of the animal centres also neutar or spay the dog before rehoming
One footnote i was recently in the vets.with my favorite Lab ,she was getting checked over after a case of mastatis after a phantom pregnancy..the vet knows shes a working dog and wanted to weigh her .The scales where in the surgery waiting room where an