汉译英:有报道说,有一个不知姓名的人救了这孩子

it's reported that an unknown man who saved the child.
楼上的UNNAMED不行

It is reported that the child was rescued by an unknown man.

It is reported that it's an unnamed people who saved this child.

it is reported that a person with unknown identiy saved the child.

It is reported that there is a person I do not know the names of the children to save

it isreported that an unkown man has saved this child.