I am just adding a summary based on my own experience.
Augusto's answer works for me but only temporarily. Just reinstall cortana. Go to powershell and type
Get-AppXPackage -Name Microsoft.Windows.Cortana | Foreach {Add-AppxPackage
-DisableDevelopmentMode -Register "$($_.InstallLocation)\AppXManifest.xml"}
After a while the stuff went the way it used to be. Sometimes, if I type zend, zend studio will show up. Sometimes not.
I am also using one of the comment as another answer in case that didn't work for you.
I found that if you go to
C:\ProgramData\Microsoft\Windows\Start Menu\Programs
and open the shortcut "Search", it opens the "Search Everywhere" feature from Win 8, and there all the apps appear, so it has to be a bug in the new search UI of win 10, and not in the indexing options. I just wish that "win + s" could open "Search Everywhere" instead of Cortana. – Augusto Barreto Aug 11 at 17:52
That is written by augusto again. BOTH of this works for me.
I did rebuilding index and other solutions. That didn't work or only work temporarily.
Thanks Augusto. I think I should add my own answer so everybody knows which solutions work in my case and probably on their cases either.