I have a content type with a field collection in it. I am using the FC table widget on the node form. I want to do some AJAX magic on the node edit form: in an AJAX callback I want to return the field collection's deltath row if a field in the deltath row changes.

So I want to wrap the deltath row in a div: 

$form['field_myfieldcollection'][LANGUAGE_NONE][$delta][#prefix] = '<div id="myfc-"'. $delta . '>';

But this does not appear in the HTML. If I change the widget to Embedded, it does.