stranger? no stranger?

From wiktionary
stranger (plural strangers)

Someone who is neither a friend nor an acquaintance.

Which means that if the person is no stranger or acquaintance, both parties should know each other, or at very least know each other's name right? Right!

But, what if he knows me but I don't? Is there a term to this?

coz some guy who knew me came to my office today for some business meeting. I happen to walk past the reception area and he called me and try to strike a conversation.

you shld see me face, I dun even remember who he is and let alone where I met him. All I could do is be polite, smile helplessly and give a 1-word answer to his question. My boss and colleagues from other department were around, and I had to pretend that I know him, else long lost "friend" will be malu.

after much thoughts, I can only conclude we must have met during partying, else I would have at least have some recollection.

I admit I'm not very good with names.
But most importantly, I don't take guys I knew from drinking seriously.
Which, by the way is the reason why most of the time I dun remember them.
I mean, how often would you bump into them again, right?
I'm not atas, but unless I know you personally, dun expect me to go over and say hi. PR-ing at work is already killing me, juz let me enjoy my stout.