Newbie question - URL parameters disappear after logging in

I'm just getting started with Drupal and would like to know how to retain the URL parameters after logging in. For example, I send users an email with a link to the Drupal site www.example.com/ticket?id=1234-567. If they're already logged into the site when they click the link, the URL parameter shows up (id=1234-567) and I can display it with PHP. However, if they aren't logged in, the URL parameter disappears after they log in (only shows www.example.com/ticket - without the id paramter).

Does this require a hack of the core modules or is there an easier way? Any help would be greatly appreciated!