I can't fault the dad at all about what happened, they laid is out really quickly that her mother's race has a unique trait that being forgotten results in death while death wipes all memories of her from the minds of others. How her daughter is still alive is a mystery but the moment he realized he had a missing child, he wasted no time in looking into it. Once he verified her identity he instantly made moves to make it official, accommodate her and to slowly gain her trust as he is painfully self aware that he still abandoned her. I honestly feel just as bad for him