flutter form data disappears when I scroll

I think the problem is that you don't save the values which were put into the TextFields (to a state for example).
From your code I assume you are using the ListView.builder() to set up your ListView. This method, as stated in the documentation, renders only the children, which are in view. Once you scroll a child out of view, it is removed from the ListView and only added again, once you scroll it into view. Because the TextField is removed, the value is removed as well.

To permanently have the value saved, I would advice to use TextFields and save the input to state in the onChanged() method of the TextField, or make use of TextEditingController.

This is because you are using ListView to render your children. ListView only renders the visible children (has recycling nature). Instead, use Column with SingleChildScrollView.

SingleChildScrollView(child:Column(children:yourFormChildren));