I'm so sorry this has happened to you. I would be just as devastated if my Frenchton Louie was lost. You have done everything possible and I hope she gets back to you. If she doesn't, I hope whoever has her is taking good care of her as I'm sure she must be a great dog to have such great parents.
My Wilsons breeder had her stud bulldog stolen and she also put flyers out but made sure she offered a reward and after 6 months someone finally snitched as to who had the dog. Other than an ear infection her bulldog was in good condition and reunited with his owner.
Hang in there.