I saw this behavior and... you know what... it's really unexplainable. I don't have a root cause (obviously) but I did resolve the problem in this way (below). I also leave a note below but I am unsure if it relates directly as to why the finder started to show results when I would search.
In general, my finder would not display any files when I opened it up and tried to make a search. Here is a picture for discussion:
What I noticed is that when I switched the button that I point to with to #2 (marked in the picture), it would show results, but if I switched to the button that I point to in #1, there would be no results.
I kept closing Finder and opening it over and over, swapping between 1 and 2. Eventually all of the different file display methods, (1, 2 and the other 2) would display results correctly when I searched for something.
I am unsure if the OS was still indexing, or there's truly a stupid bug. Check the "Note" below, because it may be related.
Note: this may not be related, but I mention it anyways... before I started playing with the Finder search, I disabled "Search Suggestions" and "Bing Web Search" by unchecking them under: System Preferences > Spotlights > Search Results.
I don't want my laptop to query the internet and use spotlight (And BING for that matter) to find things for me, if I want to make a search, i'll go to google.com.