The logic professor at Edinburgh ...
... who had taught me in the first year, met me on the way to my graduation at the end of the fourth and said "Hello, *name* congratulations on your *degree* " -- he knew the grade, the degree, and my name. I couldn't even place him. Then again I suffer from prosopagnosia - I don't recognise faces easily. I have accosted various blondes in shops thinking they were my wife; and have been caught sneakily perving at my wife thinking it was some other woman. And worst of all, I didn't recognise my dad once when he came to the door (we lived 200 miles apart and I wasn't expecting him).
On the very rare occasions I think I recognise faces, I get it hopelessly wrong. I was very pleased to have recognised someone in SW19 once, who I was convinced was one of my mature students, her face was so familiar. She wasn't but, bless her, the lady in question did not point out my mistake and chatted very amiably to me for 5 minutes or so and then, when she left, my friends wryly asked how I came to know Zoë Wanamaker.
My son has the same problem: I took him to parents evening and realized he could not recognize any of his teachers when they were at a desk in the hall rather than in their own rooms. So: if you, like many people, don't like the feeling of recognising the face but not knowing the name, spare a thought for those of us who often don't recognize people out at all!