Query Custom Fields using meta query

I can’t figure out how to query posts using meta_query when the custom field has been entered using the XYDAC fields interface.

I have a custom field ‘sticky’ which is a checkbox with label ‘Yes’. Someone would check it to ‘stick’ the post to the home page. I’m developing a widget to pull the sticky posts, but I never get any posts. Here is what I was trying:

$args = array (
	'post_type' => 'events',
	'numberposts' => 10,
	'orderby' => 'date',
	'order' => 'DESC',
	'meta_query' => array(
		array (
			'key' => 'sticky',
			'value' => 'Yes',
			'compare' => '=',
		),
	),

);
$this->posts = get_posts( $args );

In the database, when the box is checked, the meta value looks like this: a:1:{s:8:"checkbox";a:2:{s:3:"Yes";s:3:"Yes";s:10:"xydac-null";s:10:"xydac-null";}}

As a test, I created a custom field ‘test’ using the normal wordpress interface for this post type and assigned the value ‘Yes’ and was able to successfully query it using the same query above.