Today I was out on my lunch break and as always seems to be the case, someone came up to me and said, "Hey Sam!!!" I looked at him and said, "Hello there." I have never not been able to quickly identify them and respond with the "Hey Bob, long time no see," or something to that effect. But I was at a complete loss. He was dressed just like the restaurant staff so my neural connections were going haywire.
He kept talking about my work and what I was doing and then he hit a key word and then bam, I knew who it was. That puzzled look went away, or so I was told by my friend, and I was able to hold a real conversation that said I remembered who he was. He now had a wife and child and they were on the way out. We shook hands.
The question is, how long do you go before you just flat out say, "I'm sorry but I obviously have forgotten who the heck you are?"