Not to get into gender stereotypes, but was he "resting his eyes?" That's what my dad calls it when he falls asleep while in an upright or semi-upright position. He'll swear up and down that his eyes were just closed and he wasn't asleep, but the snoring gives him away. Apparently other men (to be specific, other dads) also exhibit this behavior in the wild. I don't think it's usually something they do at work, though.

Anyway, back to you... did he acknowledge what had happened? Did you? How very awkward.