Smart Group for each search term - so why so many 'Unfiled' entries?

Thanks for replying. I’m still a relative newbie, and I’m not sure I follow what you’ve said - can you clarify for a beginner?

As far as I know, what I’m tryign to do should be working. My online search results are added to ‘All references’ automatically; the searches are usually made as ‘Any field’+Contains+ " " , which is the exact same formula that the Smart Group uses to sort the main library entries, so I’ve no idea why some (most) references aren’t being filed into corresponding Smart Groups.

Any other thoughts would be gratefully received…