Face-palm moment

I've never been asked by someone whether or not I speak Chinese after I'd had three conversations with him in Chinese before. It was a novel experience. Not to mention he was a scientists from a neighboring lab and I tend to expect scientifically trained people to be ...well...more observant.

Hypotheses:

1) People really are that unobservant
2) People's power of observation are not uniform across the board
3) I am really that forgettable.

2) seems the most likely, though I'd actually prefer 3)....