As I was walking back to work from my lunch break I passed a group of four young people: two guys and two girls. I was feeling very stoic and I must've looked it (glasses on, headphones in, full speed ahead) because out of nowhere one of the girls smiled and started waving at me. She then approached me and put her hand in front of my face and offered a high-five.

This threw me off. I was in the zone and this random person approaching me definitely made me stop. I definitely looked confused.

I thought it was somebody who knew me from high school so I asked her if she was the girl I was thinking of. She said no and looked even more confused than I originally did. Like a "what the fuck this isn't what I signed up for" look.

I looked back at the group, then back to the girl and then, with a confused look on my face, reluctantly gave her the hi5.

Can anybody help me understand what was going on? What should I have done differently?