"Fatal error: Class 'mod_virtuemart_product' not found

"Fatal error: Class 'mod_virtuemart_product' not found

I tried to install my module for live searching inside of
mod_virtuemart_product module. I changed mod_virtuemart_product.xml in
this way:
Old code
<install type="module" version="1.5.0">
<name>mod_virtuemart_product</name>
<creationDate>March 17 2013</creationDate>
<author>The VirtueMart Development Team</author>
<authorUrl>http://www.virtuemart.net</authorUrl>
<copyright>Copyright (C) 2004-2012 Virtuemart Team. All rights
reserved.</copyright>
<license>http://www.gnu.org/licenses/gpl-2.0.html GNU/GPL</license>
<version>2.0.20b</version>
<description>MOD_VIRTUEMART_PRODUCT_DESC</description>
<files>
<filename
module="mod_virtuemart_product">mod_virtuemart_product.php</filename>
<filename>index.html</filename>
<filename>helper.php</filename>
<filename>tmpl/default.php</filename>
<filename>tmpl/default2.php</filename>
<filename>tmpl/default3.php</filename>
<filename>tmpl/index.html</filename>
</files>
<params addpath="/administrator/components/com_virtuemart/elements">
<param name="layout" type="filelist"
label="MOD_VIRTUEMART_PRODUCT_LAYOUT"
description="MOD_VIRTUEMART_PRODUCT_LAYOUT_DESC"
directory="/modules/mod_virtuemart_product/tmpl"
default="default" hide_default="1" hide_none="1"
stripext="1" filter="\.php$" exclude="^_" />
..
..
..
New code
<extension type="module" version="2.5" method="upgrade">
<name>mod_virtuemart_product</name>
<creationDate>March 17 2013</creationDate>
<author>The VirtueMart Development Team</author>
<authorUrl>http://www.virtuemart.net</authorUrl>
<copyright>Copyright (C) 2004-2012 Virtuemart Team. All rights
reserved.</copyright>
<license>http://www.gnu.org/licenses/gpl-2.0.html GNU/GPL</license>
<version>2.0.20b</version>
<description>MOD_VIRTUEMART_PRODUCT_DESC</description>
<files>
<filename
module="mod_virtuemart_product">mod_virtuemart_product.php</filename>
<filename>index.html</filename>
<filename>helper.php</filename>
<filename>tmpl/default.php</filename>
<filename>tmpl/index.html</filename>
<filename>tmpl/quicksearch.php</filename>
</files>
<params addpath="/administrator/components/com_virtuemart/elements">
..
..
..
And I created in mod_virtuemart_product/tmpl folder new php files and
javascript files in this way:
And I created in mod_virtuemart_product/tmpl folder new php files and
javascript files in this way:
mod_virtuemart_product/tmpl/quicksearch.php
mod_virtuemart_product/tmpl/default.php - used by virtuemart (I just add
to this code
my search input code)
mod_virtuemart_product/tmpl/head.php
mod_virtuemart_product/tmpl/config.php
mod_virtuemart_product/tmpl/js/javascript.js
mod_virtuemart_product/tmpl/css/css.css
Everything is connected. My code is functional, but when I want to add
this code to my quicksearch.php file: echo
mod_virtuemart_product::addtocart ($product);
It writes me this error:
"Fatal error: Class 'mod_virtuemart_product' not found in
/www/t/r/u46223/public_html/modules/mod_virtuemart_product/tmpl/quicksearch.php
on line 34"
Could you please advice me, what is wrong?
Thank you.