theme taxonomy term object
You are passing 'node' as the $hook value, although your data is for a taxonomy term rather than a node. Trying using the hook 'taxonomy_term' instead of 'node'. I'm not sure what the proper structure for the $variables array is, but if you have the full term object, I would try just passing $term as the second parameter. 

documentation for theme()
http://api.drupal.org/api/drupal/includes--theme.inc/function/theme/7

documentation for theme_taxonomy_term()
http://api.drupal.org/api/drupal/developer--theme.php/function/theme_taxonomy_term/7