sts_get_the_ticket_read

/**
* Returns if a ticket has been read by an agent
*
* @since     1.0.0
* @param    (int) $post_id    Post ID
* @return   (string) read/unread
*/

Returns if a ticket has been read by an agent. This information is stored in the custom field ticket-read. If this field is not empty, the ticket has been read. If no $post_id is defined, the current post ID of the loop will be used.

You can also use sts_the_ticket_read() to output the result immediatly.