Just a testcase

snarfer.php

<?php
/*
Template Name: Snarfer
*/
global $wp_query;

$old_query = $wp_query;

query_posts('author=1');
echo '<ul>';
while ( have_posts() ) :
    the_post();
    echo '<li>'.get_permalink().'</li>';
endwhile;
echo '</ul>';

wp_reset_query();

var_dump( is_page() );
var_dump( $old_query === $wp_query );

var_dump( $wp_query );