I did a search for an app in Spotlight on my new iPhone 6 Plus. I knew it existed on the phone but the search wasn’t returning it at the top of the list of search results. I fixed this by going into Settings and re-arranging the order of results. Now it appeared at the top of the results.
Next day I did the same search but it didn’t appear. Neither did any app. Very odd.
I found a page discussing this http://osxdaily.com/2014/10/26/spotlight-not-working-blank-search-results-ios-fix/
but the suggested solutions are kind of nonsensical. Like sending yourself an email would suddenly fix Spotlight. Some people think it’s RAM (it isn’t), some say scrolling through your apps then attempting the search fixes the problem.
The truth is none of these are actual fixes. What’s going on is an indexing issue. Spotlight is updating its index and there’s a bug that prevents results from being shown correctly until the index finishes.
What all of these answers have in common – and they worked for the user that tried them – is time. By the time you’ve sent yourself an email the index has finished. So, it seems as if that action has fixed Spotlight. It hasn’t. The actual answer is waiting until the index has completed.
I’m experiencing this with iOS 8.1.2 so I assume a future release will fix this.