That link isn't 100% reliable. Basically how it works is that it looks at the URL that it's coming from:
• If the URL includes the topic ID (t=####) then it knows exactly which thread to use.
• If the URL only has the post ID (p=####), however, it looks to see if it's counted a post with that ID. If that post hasn't been counted yet, then it just redirects to the main list of games.