Remember it's using a standard search engine (google by default), so instead of treating it like an index, you need to look for words that might appear in the post you're looking for. Searching on "Chambers 3D" gives a 26 June 2014 thread as first hit which might be the one you're looking for. Searching on "chamber" and "most recent topics" will mean that it's looking for posts which contain as many as possible of the words "chamber most recent topics", not looking for the most recent topics relating to chambers.