is_page_template problems & the sidebar

I’m trying to streamline my WordPress website, and for love nor money I can’t get is_page_template to work in my sidebar.php file.

This is the code I have placed in sidebar.php and loaded via <?php get_sidebar(); ?>

<?php if ( is_front_page() ) { ?>
<h3>Front Page</h3>
<?php } else if(is_page_template('event-page.php') || is_single()) { ?>
		<h3>Event Page or Single</h3>
<?php } ?>

This conditional works on the front page, and on the single pages. It just doesn’t work on the file which is named event-page.php.

Any thoughts? Could really use some help.

Thanks,
Paul