SelectUnsend for everyoneto remove the comment from the conversation, and then selectRemove.
The text you sent is gone.
In its place, a bubble says, “You unsent a message.”

This bubble is visible to all participants.
When Facebook first rolled out the unsend feature for Messenger, users had 10 minutes to remove a message.
However, Facebook removed this limitation, and you’re free to now remove messages at any point.

ChooseUnsend for Everyoneto remove the message from all chat participants' threads.
Alternatively, tapUnsend for Youto remove it from your chat but leave it on other participants' threads.
The item you unsent has “You unsent a message” in its place.

Everyone in the conversation can see this.
Why Would You Want to Unsend Facebook Messages?
Until 2018, Facebook messages could not be unsent or removed from the recipient’s inbox.

Can People Still See Unsent Facebook Messages?
Unsending a message deletes it from the conversation, so it might disappear before the recipient actually sees it.
The recipient will see that you’ve unsent a message.

To report the conversation, tap the person’s name, scroll down, and tapReport.
FAQ
kick off the Messenger app and tap yourprofile picture.
If you want to un-archive a chat, swipe left on it and tapUnarchive.

TapMoreto mark it as unread, restrict it, delete it, or block the sender.
Todelete messages on Facebook Messengerin a web app, launch Facebook, select theMessengericon >See All in Messenger.
Select a message, hover the cursor over it, and selectMore(three dots) >Remove.
In the Messenger app, tap and hold a message and tapRemove.
you might also download your Facebook data to see if the deleted messages are included.
(Go to your Messenger account configs and selectDownload Profile Information.)