At the top of Web Wiz Guide, even when you are in the forums, is a search box for site search. However, when you are in the forums, it can be confusing to new users, since they may think that the search box searches the forum as well.
I would suggest that on the results page of the Site Search in this website, mention that the site search results do not include posts in the forum. It would also be nice if you provided a link with the search terms already specified (that they just used for the site search) to search the forums.
This may explain why some people accused of not searching the forum get angry and say they did. I know before you turned on post moderation, I used to see a lot of conversations along those lines.
Also, you will need to make it obvious enough so that it won't be overlooked, perhaps in bold or a different color or something.
Search for Blah Blah in the Forums
for example.