MonoBehaviour.OnDisconnectedFromServer  

function OnDisconnectedFromServer (info : NetworkDisconnection) {
    Debug.Log("Disconnected from server: " + info);
}

using UnityEngine;
using System.Collections;

public class example : MonoBehaviour {
    void OnDisconnectedFromServer(NetworkDisconnection info) {
        Debug.Log("Disconnected from server: " + info);
    }
}

import UnityEngine
import System.Collections

class example(MonoBehaviour):

    def OnDisconnectedFromServer(info as NetworkDisconnection):
        Debug.Log(('Disconnected from server: ' + info))