That last few Lyfts I have ridden in had drivers that didn't 100% understand the English language. It's very possible they mistook the banging action as something other than "Hey, stop! I've left something in the car."
This is a horribly racist remark, basically saying that people from other countries are imbeciles with no understanding of basic human behavior. They can't speak English, but doesn't mean they have an intellectual disability and too stupid to understand what "hey stop" means.