You need to use cancel.
See working example here.
Js:
$(function() {
$('.sortable').sortable();
$('.sortable').disableSelection();
$('.sortable').sortable({ cancel: '.note' });
});
As @Zephyr points out, this let’s you re-arrange the position by dragging the siblings, if you want to avoid that, use owise1 approach:
$('.sortable').sortable({
items : ':not(.note)'
});