You were right. Google Analyticator does not place the tracking code in printer friendly pages by defaut. (this is because they don't exist but generated by WP-Print upon request and removed once the page is printed)
So this is how you can implement the tracking code in to printer friendly pages, (assuming you use WP-Print).
1. Copy and paste the tracking code into notepad and save it as "analyticstracking.php" (without the quotes)
2. Upload file "analyticstracking.php" to wp-content/plugins/wp-print
3. Open wp-content/plugins/wp-print/print-posts.php
4. Place <?php include_once("analyticstracking.php") ?> immediately after the opening <body> tag
5. Save and exit
Now every time a visitor requests a printer friendly page of a post in your blog, Analytics will log the request as /post_url/print/