Hide Uploaded Files in File Field in Node Edit Form
Create a custom module and implements hooK_form_alter(). and set field access to false for other user except administrator.


function MODULENAME_form_alter(&$form, &$form_state, $form_id) {
  global $user;    
  if ($form_id === 'CONTENTTYPE_node_form' && !in_array('administrator', $user->roles) && $form['field_image']['und'][0]['#default_value']['fid'] > 0) {
    $form['field_image']['#access'] = FALSE;    
  }
}


MODULENAME = Your costom module machine name.
CONTENTTYPE = Your content type machine name.
field_image = Your custom file field machine name.