I actually just ended up doing a hook_form_alter and adding a submit handler that saved the referenced field value from the form state into the field that I wanted to save it in on the non referenced node.
This worked nicely, but you had to save the node before it updates and you have to make sure to tell the web admins that the date field won't update until after they save the node. This provided a little confusion at the beginning.
So, this is a great solution for any node where you want to save form state data from one node/entity to another and have a unique identifier like nid/gid to do database lookup and save. Code sample below. I realize that node_load might be expensive to do, but since it's only happens when an admin user saves a form, I thought it was alright.
/**
* Implements hook_form_alter().
*/
function custom_add_survey_date_form_webform_node_form_alter(&$form, &$form_state, $form_id) {
//Add submit handler to grab and change date values
$form['#submit'][] = 'custom_add_survey_date_submit_handler';
}
/**
* Adds a submit handler to webform_node_form
*/
function custom_add_survey_date_submit_handler($form, &$form_state) {
//grab reference to event date
$og_reference = $form_state['values']['og_group_ref']['und'][0]['target_id'];
//load date from event plan node
$og_node = node_load($og_reference);
$event_date = $og_node->field_date_of_event['und'][0]['value'];
//Store date on survey node
$form_state['values']['field_date_of_event02']['und'][0]['value'] = $event_date;
}