The logo being the part of the header is placed in the header itself. But if you want you can replace the logo anywhere in the theme, i.e. before header, after header or even in the sidebar.
In one of the recent projects we had a chance to experiment with adding the logo in the sidebar. And here is the code for the same. Fire up custom_functions.php and add the following code:
function sb_header()
{
?>
<p id="logo"><a href="<?php bloginfo('url'); ?>"><?php bloginfo('name'); ?></a></p>
<h1 id="tagline"><?php bloginfo('description'); ?></h1>
<?php
}
remove_action('thesis_hook_header', 'thesis_default_header');
add_action('thesis_hook_before_sidebar_1', 'sb_header');
The above code actually replaces the default Thesis header (which includes the logo & tagline) with its exact replica which is required to be placed at a different location. So first you need to remove the default header with remove_action() and then you add the logo and tagline to new location (sidebar in this case) as the second step.
Have you tried to relocate the logo in your theme?