Loading Assets from inside of theme folder

[eluser]xtremer360[/eluser]
I added this to my default.php file in my layouts folder and nothing gets echoed and I have no idea why.

<?php echo Asset::css('bootstrap/bootstrap.min.css'); ?>

I have this in my file system.

/application
/themes
/supr
/views
dashboard.php
login.php
/layouts
default.php
/parials
header.php
footer.php
breadcrumbs.php
sidebar.php
/assets
/js
/css
/bootstrap
bootstrap.min.css
/images
/public_html
/assets
/js
/css
/images
index.php