Answer by  
                                                                                          freebird (225)
                                                            
                          
                          
                                                          Don't sneak away.  Tell him you are leaving, and then leave.  Wait a minute, then come back.  Tell him, "See, I told you I'd come right back."  Next, leave him for a few minutes with a trusted relative, repeating that you're leaving and then now you're back.  He'll slowly learn to trust that you will, indeed, come back when expected.