Embarassing moments with random people?

I was at the mall one giorno with my mom, and she saw one of the ladies she used to work with 15 years ago, so they stopped and detto their hellos and all that. My mom mentioned that I had just graduated from high school the night before, and the lady was like "Oh congratulations! From which school?" I detto the name of my school and she was like "Oh yeah they're our rivals we dont like them blah blah blah". But she was just playing around, so she made that 'Oh Im just joking with you' gesture with her hand [or wrist, I guess], and I thought she was giving me a high 5 so I put my hand up to her hand, but it just looked like I was pushing her away and like I didn't want her to touch o come near me...
I felt soooo awkward just standing there while they continued to talk to each other, I was so embarassed! Her daughter was standing across from me looking at me all weird and stuff I was thinking oh my gosh.... I felt so dumb! I guess I could have detto "I thought te were giving me a high five" but that probably would have made things even più awkward. But I laugh about it now :]

So have te had any embarassing moments with random people o people te don't really know?
<3