did not recognize a friend's voice

I pride myself in knowing who people are by their voices. I'm good at it generally. I don't need to have met a person very many times before I know who they are. If they call me by phone, I know them almost right away by their voices. So, I was pretty embarrassed recently to meet a friend (a very good one at that) and not know her by her voice. In my defense, I wasn't expecting to meet her on the sidewalk as I did. She thought it was funny when I asked who she was. I was really embarrassed. But, when I meet someone out of context like that, I sometimes get confused. I suppose this happens to sighted folks too?