Can you please provide us with screenshot ? Or steps to reproduce this?
Also check if there is some Console error and error in AEM Error.log ?
I don't know if you have solved this issue yet; but I had the same issue and after comparing my prod and dev environments, I noticed this path was missing " /conf/global/settings/dam/search/facets/assets/jcr:content" in my dev environment for some reason. I created a package for that path and uploaded it to my dev instance and my issue was resolved.
Hopefully this helps you or others if they run into a similar problem.
This exact same thing has happened to me. The Assets Admin Search Rail has just disappeared and I only get the search text box on searches.
Thanks to kautuksahni , I packaged up what I had on staging in: /conf/global/settings/dam/search/facets/assets/jcr:content , and uploaded it to production and it fixed this issue.
Scary why it would all of a sudden disappear like that, but at least there is a fix to it.
Hope this helps.