How do I load the $form_state for a form loaded with drupal_get_form?
When you do drupal_get_form() the form and state is cached, otherwise other Drupal form functions wouldn't be able to get it back later.

The only way I know to get it is like this:

// Get the form.
$form = drupal_get_form('my_form_id');
// Get the default form state.
$form_state = form_state_defaults();
// Get the form and form state from the cache for the form you just got.
form_get_cache($form['#build_id'], $form_state);


Since form_get_cache() returns the form also you could do the last line like this:

$form = form_get_cache($form['#build_id'], $form_state);


and it would overwrite your form with the cached one and update your form state (since $form_state is passed by reference) but in the case of calling it right after drupal_get_form() there is no need to do that.