If I have understood you clearly, when you input ANY term in the search field in File Explorer and press return, the advanced search tab fails to appear?
If so I would add your comments in the feedback Hub and also open a case via settings/get help. Just put random rubbish in the message field until the option to chat to a person appears. They will hopefully offer you a remote session.
I also have a works laptop which is still operating on creator version 1806 where the search filed is intact and working as it should be. I couldn't roll back to this version as I was on v.2004.
If u are on version 1909 you can roll back.
However unless you have somehow disabled the automatic updates (i dont know how to do this ) this would be very much a short term resolution as your machine will eventually update.