If you search the forum using the box on the right while you are viewing a thread you will get “No Results Were Found”. If you click the “Search Again” button on that page then you will get the results.
If you use the box from the main page of the forum, where the list of threads are listed , the search box works.
I think the problem is that for some reason the search box pass the id of the thread from where you made the search. I don’t understand why the search needs the id but anyway this is the link generated by the search box from within a forum thread:http://themeforest.net/old_search?utf8=%E2%9C%93&term=collins&type=forums&type_id=thread%3A77051
and this is the link generated by the search box from the main page of the forum:http://themeforest.net/old_search?utf8=%E2%9C%93&term=collins&type=forums&type_id=
As I understand in first case it search in the Forum Area (Notices, All Marcetplaces, Item Discussions etc) where your thread is located.
If there is no result in this area you gets empty search results page (your first link)
Then you click ‘Search again” and it search through the selected area in “Search In” drop-down
verified now. It appears it will search first the thread you are reading at that moment. if it finds some results it will return the post where that term is mentioned, if not you get no results.
So is not a bug but probably work in progress. Maybe the search box will get pertinent description “search within the thread” later on.