I don't see that behavior.
1) go to the demo library http://charles.the-haleys.org/calibre/demo/
2) search for khalid. You will find one book, The Book of Khalid
3) search for Rohmer. You will find 14 books, none of which is the Book of Khalid.
I can't explain why your system is behaving the way you describe.
Noticed that your server doesn't have this problem.
Just browsed through my log files. Seems to be a smarty problem on my side: Undefined variable: _SESSION in /usr/share/php/smarty/Smarty.class.php that keeps popping up. Will look further from here. Thanks for the quick reply!