Yesterday my daughter, and I were talking about how her boyfriend's dad was upset, because my husband didn't stop and chat with him at our local supermarket the other day. He thought it was rude, but I know it was that my husband was in a hurry, and didn't think about it. I know this because it's very unusual for my husband to see someone he knows out in public, and not stop, and have a long chat. Since he owns his own business, and meets lots of people this happens all the time.
Then my daughter says to me, "Mr. S. (her computer teacher) said that he's seen you at the store a few times, and he said hi to you, but you didn't respond. I told him you just don't really notice people."
I never heard, or saw him.