Step 5: After submitting to Facebook, wait a few days, then go back to your block list (Remember the step in which you were supposed to take a screenshot of all the names or write them down?) compare your new block list to the previous one. There will be a new name added to the list, that person is the one reporting you.
Basically, after Facebook receives the message you sent them, they block the person who reported the post for you. if you don’t have anyone blocked on Facebook, then you’ll realize that suddenly, there’s one person on your block list – That person is the reporter. If you have hundreds of people blocked, then you’re going to have a hard time figuring out who is new on your block list, but with dedication, you’ll find him eventually.