Check If Posts Exists?

How can I check if a post exists, outside the Loop?

I’m trying to conditionally display a post using the Get A Post plugin. If the post doesn’t exist, I don’t want the DIV to display:

<?php $announcement = get_post(27);
         if ($announcement) { ?>
            <div id="announcements">
			<?php get_a_post(27);
                              the_content(); ?>
		</div>
	<?php } ?>

This returns “Fatal error: Cannot pass parameter 1 by reference”

Searched everywhere in here but didn’t find a solution. Thanks in advance!