on form submit user session data is lost - forms

Question

I am working on a codeigniter listing application, everything is working fine in the application but when I am submitting the listing form, the user session data is lost.
I am having: agentId in session, which is visible after login but after submitting it is not in the session data.
Code:
$agentId = $this->session->userdata('agentId');
var_dump($this->session->userdata);
die;
\\ This session showing all user data including agentId
$data['p_title'] = $this->project_model->projectName().' :: Property : Add New Property';
$data['Message'] = '';
$data['heading'] = 'Property: Add New Property';
$data['pageName'] = 'property';
$data['title'] = filter_value('title', '');
$data['meta_decription'] = filter_value('meta_decription', '');
$data['keywords'] = filter_value('keywords', '');
$data['type'] = filter_value('type', '');
$data['sub_type'] = filter_value('sub_type', '');
//$data['sub_type1'] = filter_value('sub_type1', '');
$data['bedrooms'] = filter_value('bedrooms', '');
$data['kitchen'] = filter_value('kitchen', '');
$data['parking'] = filter_value('parking', 'YES');
$data['bathrooms'] = filter_value('bathrooms', '');
$data['area'] = filter_value('area', '');
$data['price'] = filter_value('price', '0.00');
$data['location'] = filter_value('location', '');
$data['city'] = filter_value('city', 82);
$data['country'] = filter_value('country', 102);
$data['details'] = filter_value('details', '');
$data['featured'] = filter_value('featured', 'NO');
$data['countries'] = $this->general_model->listCountries($data['country']);
$data['cities'] = $this->general_model->listCities($data['country'], $data['city']);
$this->form_validation->set_rules('title', 'Property title', 'trim|required');
if($this->form_validation->run() === TRUE){
$agentId = $this->session->userdata('agentId');
var_dump($this->session->userdata);
die;
\\ but here the agent id and rest of user session data is removed.
$Date = getCurrentDate();
$Time = getCurrentTime();
$DbFieldsAry = array('agentId', 'title', 'meta_decription', 'keywords', 'type', 'sub_type', 'bedrooms', 'kitchen', 'parking', 'bathrooms', 'area', 'price', 'location', 'city', 'country', 'details', 'featured', 'date');
$InfoAry = array($this->session->userdata('agentId'), $data['title'], $data['meta_decription'], $data['keywords'], $data['type'], $data['sub_type'], $data['bedrooms'], $data['kitchen'], $data['parking'], $data['bathrooms'], $data['area'], $data['price'], $data['location'], $data['city'], $data['country'], $data['details'], $data['featured'], $Date);
if($this->general_model->addInfo_Simple($DbFieldsAry, $InfoAry, 'tbl_properties_list')){
$activityId = $this->general_model->getSingleValue($data['title'], 'title', 'property_id', 'tbl_properties_list');
setMessage('success_message', 'New property added successfully. Add pictures to property.');
redirect(base_url().'property/update/'.$activityId.'/0', 'refresh');
}
else{
setMessage('error_message', 'Unable to perofrm this operation, please try again later!');
redirect(base_url().'property/user_listing', 'refresh');
}
}
$data['allowed'] = true;
$data['warning'] = '';
if(!isSuperAdmin()){
$total_properties = $this->general_model->getTotalDataSimple1('property_id','tbl_properties_list');
if(allowed_properties() <= $total_properties){
$data['allowed'] = false;
$data['warning'] = '<br/>You have reached to maximum limit of your property upload listing.<br/>Click HERE to change payment plan.<br/><br/><br/><br/><br/>';
}
}
$this->load->view('add_property', $data);
The first var_dump for session check shows all session data, but why is all the user session data lost after submitting?