I ran into this SharePoint 2013 search problem today. Search center worked correctly returning lots of results. Search service was crowling content correctly, lots of elements in index. But if I used “Find a file” on any document library, it was returning nothing, with message:
“Your search returned no results.”
Some files might be hidden. Include these in your search
These files were indexed and searchable, I was able to find them in Search Centre search results page.
Web Application was on http://intranet.domain.com and AAM was https://intranet.domain.com for Extranet zone.
In Content Sources in Search Service Settings, I notice that start address specified is actually https://intranet.domain.com Someone just put it there assuming that this is the only site address. WRONG.
This is not correct, URL should be pointing to the default zone http://intranet.domain.com
I changed that, reseted index, recrawled and after that I finally enjoy in place search results.
I hope this will help you as I did not find much info on this problem on the net so far.