ZD search bar only searches on title, and does not show there may be other relevant results. Only when you select 'enter' do you see there may be many more results -- because the search on the full page now searches across title and text. 

I'd suggest adjusting the search preview to align with the full search results behavior. 
That said, at a minimum, there should be a 'see more results' result at the bottom of the search suggestions, indicating to the user they may find what they need even if it doesn't display initially.