Theme search form: search-theme-form.tpl.php (Zen)

Hi

I'm trying to create a theme based on the zen theme. I want to change the HTML that displays the theme's search box (replace the button with a link). The handbook tells me to copy search-theme-form.tpl.php from the main zen directory to my subtheme's directory and uncomment the function SUBTHEME_search_theme_form() in template.php. template.php has no such file (not in the release, nor in the development version).

There is a function called phptemplate_search_theme_form($form), but when I uncomment that, it just takes the search-theme-form from the zen directory, not the one from my subdirectory. How do I make it use the search-theme-form in my directory, and what happened to the function that the handbook talks about?