@mysweetwhitedog,

If it's a long thread, there will probably be multiple pages for the thread.

1. Scroll down to the bottom of the page.
2. Where it says something like this:       Previous    1      2      3      4      5      Next   , click onto the last page. (In this example, 5 is the last page.)
3. Scroll down the page to the last post.

Also, you may want to check the forum settings that you have. Under My Settings, in Preferences, in the Linear Layout tab, you can decide upon the number of topics per page and the number of posts per page that you view in a topic. Make sure that Jump to first unread post in a topic is checked.  In the Threaded Layout tab, you'll see relevant options if that's what you are using.