MonoBehaviour.OnPlayerDisconnected(NetworkPlayer)

Description

Called on the server whenever a player disconnected from the server.

using UnityEngine;
using System.Collections;

public class ExampleClass : MonoBehaviour {
    void OnPlayerDisconnected(NetworkPlayer player) {
        Debug.Log("Clean up after player " + player);
        Network.RemoveRPCs(player);
        Network.DestroyPlayerObjects(player);
    }
}