Contact form redirects to homepage without showing submission information
You can use hook_form_alter to hook into the contact form and change the default submit behaviour. So instead of redirecting when the form submits, you can just omit that part and display the status message.

function mymodule_form_alter($form, &amp;$form_state, $form_id ) {
  if ($form_id == 'contact_site_form') {
    // Use our own custom submit function for the contact form.
    $form['#submit'] = array('my_custom_submit');
  }
}

function my_custom_submit($form, &amp;$form_state) {
  drupal_set_message(t('Success.'));
}