Is it possible to hypnotize someone unknowingly?

A few years ago I think I unknowingly hypnotized a lady at a gas station when I woke up sleep deprized with wide eyes and pupils. I think my blank stare may have hypnotized her because she ended up giving me back 120 dollars when I was getting gas and I counted it and told her that her manager won't be happy when he sees you gave free gas and extra money back.