failure displaying error msg

[Ranyhoss72]

My problem are:
i.when i run the system statement 'USER ALREADY EXIST' not displayed when i try to register user with the same no_staf (staff number) which exist in database.

ii. registration with the same no_staf does not go through which mean, the code prevent re-registration of existing user but not sure why above statement not displayed

hope somebody can correct me.

public function daftar()//register new account/user
	{
		$this->load->view('view-daftar-akaun'); //view register account
	}
	
	public function daftar_akaun()//register account
	
	{
	
		$query = $this->modeluser->ciptaAkaun();//create account
		
		
		$this->session->set_flashdata('mesej', '<span class="label label-info">Akaun telah berjaya dicipta!</span> ');
		redirect(base_url().'admin/daftar'); 
	}

model

class ModelUser extends CI_Model {
	
	public function ciptaAkaun()
	{
		
		$namaStaf 	= 	$_POST['nama_staf'];//staff name
		$noStaf		= 	$_POST['no_staf'];// staff number
		$email 		= 	$_POST['email'];
		$kataLaluan =	sha1($_POST['kata_laluan']);
		$jenis 		= 	0;	// user is 0 - admin is 1
		$jawatan	=	$_POST['jawatan'];
		
							if ($this->checkUserExist($noStaf ) == false)
            return 'USER ALREADY EXIST';
			 
	 $this->db->query("INSERT INTO akaun (nama_staf,no_staf,email,kata_laluan,jenis,jawatan) VALUES ('$namaStaf','$noStaf','$email','$kataLaluan','$jenis','$jawatan')");
    }

 private function checkUserExist($noStaf )

  {
     $this->db->where('no_staf', $noStaf );
     $query = $this->db->get('akaun');
     if( $query->num_rows() == 0 ){ return TRUE; } else { return FALSE; }
  }