Hook_theme in module not working
Your only defining the function, your not calling it.

   print theme('vimn_article_template', $vars);


Think you also have to implement hook_theme_registry_alter() for Drupal to pick up your template.

Maybe you can use a process function to assign this to a variable for the template.

function YOURMODULE_preprocess_HOOK($variables) {
   $output = theme('vimn_article_template', $vars);
   // etc, etc...
}