Unless your LW preferences are partially corrupted, it suggests the file you saw in search results does not have 100% identical download hash even though it's basically the same file. However in your scenario, it does sound like something is amiss. If your incomplete files keep disappearing from the download window by themselves & you are continually forced to resume them from the library window then something is definitely wrong. In that scenario then yes LW has not initially detected the incomplete proper download hash (until you have resumed the file from Library incomplete folder or pressed download from the search results) & thus cannot compare such to search results. Hope that makes sense.