Today I made the fatal mistake of updating my Windows Plex app (and not Plex Server) to the new search feature. 
If anyone else does the same, simply download this version to rollback:
If you want a different version, you can replace the URL with any including:
1.37.0.2706-5b2cfe50
1.38.0.2734-ec4489fe
1.39.1.2763-300bb607
I really do hope Plex can prioritise bringing back the old search page, as others have pointed out including most recently @jonnyatlas there are quite a few scenarios that are now broken.
