Fields are attached to Entities, not Nodes. So the field is either attached to bundle that is your node (for all nodes, pre-existing or not), or it hasnt been attached to that bundle yet.

You can use [field_info_field][1] and look at the element `bundles` to see if your given field is attached to the given Entity. If it isn't you can use [field_create_instance][2] to add the field to your entity.

You can get a list of all entity types and inspect their bundle types with the `bundles` key returned from [entity_get_info][3] by calling `$site_entity_list = entity_get_info(NULL)`.

Entities and fields are cached, so be sure you use something like `drush cc all` to be sure you're looking at up-to-date values for all these function calls.


  [1]: http://api.drupal.org/api/drupal/modules!field!field.info.inc/function/field_info_field/7
  [2]: http://api.drupal.org/api/drupal/modules!field!field.crud.inc/function/field_create_instance/7
  [3]: http://api.drupal.org/api/drupal/includes!common.inc/function/entity_get_info/7