Does sometimes any person contact you by private message in facebook ( or in another social media ) but you honestly don't remember who he is but that person says he knows you because he met you a long time ago? Despite you can't remember him but however all the information he provides turn out to be all verifiable at the end ( such as by confirmation from eyewitnesses ( from your relatives or some people you know ), even by photos he has, etc. Do you believe him in that case?