If you mainly use the iOS or Android app for Messenger, then start by launching the app. Then, tap on your profile picture and you should see an option which says “Message Requests”.
Choose this and then you will be greeted with two options – “You May Know” and “Spam”. Click on either of these to see potential spam messages, or messages from people you might know …but aren’t yet friends with. This could include competitions you’ve entered from sponsored pages and more.
On the desktop version of Facebook, you’ll need to follow similar steps to access this hidden message folder.
First, head to the Facebook website and log in. Then, click on the Messenger icon in the top right hand corner and then choose options. This appears as the three dot icon. After that, select Message Requests.
Like with the Android and iOS apps for Messenger, once you choose this option you’ll see all the messages in your secret DM folder.