Today the "The threads below have not been updated since your last visit but still contain unread posts." text has always been appearing at the beginning of the search results, even when there clearly are threads that have been updated since my last visit. I've tried logout/in to reset cookies but the same result.
I suspect you may have forgotten the code to overlook the stickies when scanning down the list to find the first post before the last login (or perhaps I have completely mis-guessed how you build the frame).