I received a message on Facebook, but the name is just “Facebook user” so I don’t know who it is. How do I find out?
hackers or the people stays in ur atmosphere..hav fun.
The user has blocked or deactivated his or her profile after sending you the message! so there is no way to find out who he/she is unless he/she unblocks/reactivate the profile..
Maybe there is a clue in the inspect elements?
it might be a spam or the account has been deleted by facebook.
As another user has pointed out it was probably a spam message which was sent to a lot of people. These people probably reported it as spam and Facebook deactivated the account. The "Facebook user" moniker is probably just a fallback default name for accounts that have been purged.
Unless it was a message that was targeted directly at you (i.e. it mentioned your name) this is the most likely explanation.
its probably just a spam account. just report it. https://www.facebook.com/help/205730929485170/
How can I find out the source of a threatening Facebook message?
Click on the name, it should take you to the page and hopefully a few details.
Why don't you ask the "facebook user" who he is?