How to Recover Deleted Messages on Facebook Messenger
If you deleted a message on Facebook Messenger, there are several things you can try to do in order to recover that message.
As long as the message still exists on the Facebook server, you can still get it back.
Option 1: Check your archive and hidden messages. Lot of times, the message is not deleted and you can still find it in the other messenger tabs.
Option 2: Check email notifications. If your notifications are on, Facebook sends you emails when you get Facebook messages. So check the email connected to Facebook to see if you see that notification.
Option 3: Request Facebook to send you your Facebook Data. Facebook keeps everything you've ever done on Facebook and as long as the messages remain on their server, that will be part of the archive data that you can request and download.