Oh sorry for the big delay!
I know your issue and it's somehow a problem with some themes/frameworks and their implementing of a search results page. To complicate things even more their are some issues with the bbPress templating for search results. I've been collecting patches and user feedback for the last few months and weeks and might finally address all of these things in a new version of the plugin.
In the meantime you can use these 2 free plugins that might help you:
--> Can fine tune your search results, sorting chronologically - and it works for custom post types like bbPress uses them
--> this plugin is especially for bbPress 2.x and should work really fine - it doesn't use a select drop down for forum/topic types and it combines forum results with results from your whole WP powered site. But all in all it's a great plugin!
I hope this helps for now!
Of course, I'll notify also here in the forum if a new version of my plugin becomes available.
Thanx for using or trying out my plugin!