functions.php

function temporary_fix_product_search( $where ) {
	global $pagenow, $wpdb, $wp;

	if ( 'edit.php' != $pagenow || ! is_search() || ! isset( $wp->query_vars['s'] ) || 'product' != $wp->query_vars['post_type'] ) {
		return $where;
	}

	$where = str_replace( "post_type = ' '", "post_type = 'product'", $where );
	return $where;
}
add_filter( 'posts_search', 'temporary_fix_product_search', 20 );