$query->num_rows nothing returns

Within my model I have the following code but does not return anything (running the sql in the bank returns the record).
 
I also tried with $ query-> num_rows also, same thing ... what's wrong?

Code:

<?php
class login_model extends CI_Model{

function ValidaLogin()
{

$query = $this->db->query("SELECT * FROM `usuario` WHERE `Usuario` = 'user' AND `Senha` = 'password'");

if ($query->num_rows() > 0)
{
  foreach ($query->result() as $row)
  {
     echo $row->usuario;
  }
}

Maybe you should add value for "FALSE" logic. Like this :
if($query->num_rows() > 0){
 //code if result not empty
}else{
  return FALSE;
}