blasts from the past

are all well and good but what if you cant remember them? Im in a bind and in need of advice. I recieved an email today courtesy of Friends Reunited ( who uses them anymore anyway? everyones on Facebook!) 'Hi Kel, hows things... think of you and your family often...signed X. Nice, love tracking people down myself and love being 'found'. Problem is, in this case i have absoloutely no idea who this person X is. Its embarrasing and a little worrying. Was i really as good a friend with this person as the tone of their mail implied? or just how fickle was I as a teen? Or, is it possible that they found more in me than I of them at the time and so remembered me more? I dunno. Its all a bit trippy. My problem is now, I have no idea of the best way to respond. Do i tell them straight up that I have absoloutely no remote idea who they are? that seems so cruel. So brutal. So, not me. But to send back a benign mail in the hope of garnering more information and therefore jog my memory, without referencing my dilemma seems dishonest. Anyone else had this problem? How would you handle it? Sheesh. This is such a farking new age, social networking, techie problem.