Only hope at this point would be Familial DNA matching .....? If she was taken by the couple and raised as their own ....then she might have children /grandkids who are registered on GeD match or the other find your family tree ancestry sites ?
I think if she lived on .....she grew up not remembering the first 21 months and doesn't know she was kidnapped ........
Hoping for the couple taking her to raise as their own as best outcome ...stuff like human trafficking would not have existed even in 1960 , right ? :-(