You're missing the point. The cult leaders controlled the courts, police, school board, and most medical facilities in the Utah and Arizona counties where the main communities are located (and to a large extent still do). The documents would "check out" just fine, even if they contained false information, because they would have been issued with false information.
So on that basis the official documents are presumed to be illegitimate and adult women can be held indefinitely? Or does Texas have a duty to recognize the official acts of other states, as mandated by the Constitution? The legal presumptions of innocence are intended to protect the innocent. They are not to be ignored by anybody simply because they have suspicions.
For how long are you willing to detain an adult woman against her will in order to prosecute a rape you suspect was committed against her?