When you're viewing questions tagged with one of app,script,library, you get the special formatting view with the thumbnail on the left. On pages where this view is displayed, only one of these tags will be shown even in cases where more than one is present. This is likely by design, and it's debatable whether a post should be tagged with more than one thing from this list to begin with.
However, the page doesn't seem to try and pick the right tag to display, like in this example from the list of questions tagged library:
Something similar happens if you search for the intersection of app and library. This seems to be the only example of this occurring, but since any user can create this scenario, it would be nice if the page handled it properly or the multi-special-required tagging was prevented.