I searched for some episodes of a tv show, and I stopped the search when I saw the first few episodes. I downloaded the first few episodes, and even though I saw all of the episodes availiable for download, I figured I could always come back. Well, I searched for the exact same thing later, and the results were narrower, with none of the same ones I saw before. I searched again, after disconnecting and connecting, and that time there were no results. I know the episodes are there somewhere...why don't they show up when I search?

Time of day perhaps. People come & go from the network all the time. Yes even 30 mins can make a big difference. My advice is, right-click the search results tab & choose "Get More Results".