It could be your junk filter at work. It is detecting junk & so it appears in the screen for a moment & then disappears. If you want to be sure the junk filter is filtering out the correct stuff, go to LW's menu bar, Tools>Options>Filters>Junk & set it to show at bottom of results. So then you can check. If there's anything that has the trash icon that you know for sure is not junk, then select it & press the trash icon button to designate it's not junk.