"Who Are You?"

It is SO awkward when somebody comes up to you with a big smile and a buoyant greeting and a hug/handshake ... and you don't know who they are. And then you embarrass yourself and ask, and find out it's somebody you obviously should've recognized, except he's aged a LOT since you last saw him and that's why you didn't recognize him. When it happened today, at least I had the sense to bite my tongue and refrain from blurting out why I didn't know who he was.