hi,
try this;
open this PHP file:
/templates/YOUR_TEMPLATE/html/mod_virtuemart_search/default.php
and just before </form> line, enter this line:
<input type="hidden" name="Itemid" value="339" />
Since the form is submitted via GET request; you can also try adding this Itemid variable to form action URL, something like this:
<form action="<?php echo JRoute::_('index.php?option=com_virtuemart&view=category&search=true&limitstart=0&Itemid=339' ); ?>" method="get">
regards.
Support