How to enable missing tag search in Spotlight? OS X Mavericks adds better support for tags. You can search tagged files using Spotlight with the query tag:tagname. 

However, this stopped working for me a few days after upgrading form OS X Mountain Lion. Whatever I search for, no results. My tagged files are still tagged and I can use them via OS X’s “smart folders“ and third-party tools. It even works in Finder windows when entering only tagname and choosing the proposed tag. I use OS X 10.9 (13A603).

Is there any switch to enable it in the Spotlight dialogue again or could it just be a bug or even a known issue? I haven’t found anything so far. 

Thank you for your help.
I don't know the definitive answer, but we could usually solve these issues by rebuilding the spotlight index. Takes a couple of hours, but most issues are fixed that way:

sudo mdutil -E / #deletes the spotlight index
sudo mdutil -i on / # starts the reindexing process


Additionally, you can use the commands here for an even more lowlevel approach