Not sure if it’s related, but here goes:
I’m not using Recent Topics and Private and Hidden forums does not appear in search results for me.
I do however have a couple of “private” forums that I’m restricting access to with the “Members” + “Tehnik BBPress Permissions” plugins, and with those the protected posts and replies appear in the search results.
I’m also using “bbPress – Private Replies” and “bbPress – Private Topics” (same as “Private Replies” but modified to work on topics) and that combo is able to hide the private content from the search result.
Another equally serious problem is that when a user uploads and attaches confidential images or data to a post and marks the post as private, the post is correctly hidden but the files are accessible to all users in the media manager. I have been unable to restrict access to the media manager.