We've noticed some missing threads from time to time that we have no explanation for. But there are many that may be hidden from view depending on what your viewing preferences are. In each Forum there is a dropdown box near the top right that is set by default to only display topics from the last 100 Days. You can change that at any time to display older topics or even All Topics. This will only affect this one visit. I believe that there is a setting in your preferences area which could make the change permanent.