What is the syntax for using a token on webform confirmation page for Drupal 7 Webform 4
Use Webform tokens module


  Webform Tokens provides tokens for user form submissions for forms
  created with the module Webform 3.


But Webform4 has this feature inbuilt, you might try this patch to fix it.

OR

You can try writing webform-confirmation.tpl.php to achieve the same.