Prevent data loss in MQTT When the broker goes down for some time

Question

So, If the broker goes down for lets say 20 seconds and comes back up and I have published something, there will be data loss. I have tried adding Qos as 2 and retain = true but only the last message is displayed i.e. If I enter 1,2,3 when broker is down then only 3 will be shown! Tried similar queries on StackOverflow but only worked while printing the last previous data!

This is what I have tried and understood till now using MQTT. But I still don't know how to prevent data loss!

Publisher ==>

import paho.mqtt.client as mqtt

# MQTT broker details
broker_address = "localhost"
port = 1883

client = mqtt.Client()

client.connect(broker_address, port, 60)
client.loop_start()

while True:
    message = input("Enter message to publish (or 'q' to quit): ")
    if message == 'q':
        break
    client.publish("mytestingtopic", message, retain=True, qos=2) 

Subscriber =>

import paho.mqtt.client as mqtt
import time

broker_address = "localhost"
port = 1883

def on_connect(client, userdata, flags, rc):
    # print("Connected with result code " + str(rc))
    client.subscribe("mytestingtopic", qos=2)

def on_message(client, userdata, msg):
    print("Received message: " + msg.topic + " " + str(msg.payload))

# Create MQTT client
client = mqtt.Client()
client.on_connect = on_connect
client.on_message = on_message

while True:
    try:
        client.connect(broker_address, port, 60)
        client.loop_start()
        while True:
            pass
    except KeyboardInterrupt:
        client.loop_stop()
        break
    except Exception as e:
        print("Error: " + str(e))
        time.sleep(5)