Accessing location field programmatically in Drupal 7, via hosting entity object and wrapper
For a custom field to be available to the wrapper, the module defining it needs to implement hook_entity_property_info() (or, which is new to me, by adding property metadata to the field using hook_field_info_alter()).

The location_cck module doesn't do that, but the bundled location_entity module does. 

If you enable that module you should be able to access the location field as you'd expect.