The reason is that at the moment, Facebook has not included a feature that allows its users to retrieve deleted messages on the social networking site. So if you’ve actually deleted a particular message on Facebook, we will teach you how you can retrieve it from other locations.
Archived Messages on Facebook Messenger
If you archive a Facebook message, you didn’t delete it. If in the process of trying to delete a Facebook message you then click on the “X” button, you’ve archived the message not deleting it. Archived Facebook messages can be retrieved. To retrieve your archived messages, click on the more button, scroll down the drop-down menu in your Messenger inbox and then click Archived. Once you do that, you’ll see all the messages you’ve archived.
Hopefully, you’ll find your message here. (Alternatively, you can search the contact’s name in the search bar, and your full conversation history should pop up.). However, if the message isn’t in the archived messages, it then means you’ve actually deleted it.
To retrieve the message will now require you to contact a third-party. The third party here refers to the person you converses with. If you’re fortunate, the person hasn’t deleted it, good. Request the person to re-send the message to you.
Now that you’ve succeeded in getting the message from your friend, the question now is how do you prevent this mistake from re-occurring in the future. Well, to prevent this ugly scenario from occurring again, archive your messages rather than deleting it. When you archived your message, you can always retrieve it back by going to archived messages.
How to archive a message on Facebook
To archive message/conversation on Facebook, while in the conversation box, click on the gear-shaped icon and select archive from the drop-down menu.
How Do I View/Retrieve Deleted Facebook Messages?