When blocking a user on the forums, their posts are completely removed from your view. There is no magic link to expand their "hidden" posts unlike phpBB/etc. No, their posts no longer are seen entirely. This is retroactive, and the recent posts list will update showing no sign they ever existed, ever, on the forums.
Just be careful with this feature on the forums. You can unblock users by going to your user page, and clicking "More" then choosing the "Blocks" option. Go to their user page and then click on "More" then click on "Unblock User."