title: Observe reference removal
body: <p>I have a very simple question.</p>
  
  <p>I have a reference like this : /myref for which I set a value for example : "Hello"</p>
  
  <p>And I want to listen when the myref reference is removed.</p>
  
  <p>I tried observeSingleEvent Child Removed but it is not triggered as there is no child.
  And I don't want to listen the parent reference until the child removed is myref.</p>
  
  <p>Do you have any solution ?</p>
  
  <p>Thanking you in advance.</p>