I did not know paper tickets had to be validated on a Warsaw tram

I got on a Warsaw tram on Thursday morning with a paper ticket and no idea that it had to be validated on board. A woman next to me took my ticket without a word, held it up, and pointed at the validator by the door. A minute later two inspectors came through the tram. I would have paid a fine bigger than my dinner. I thanked her in Polish, which is to say I said it wrong. She nodded as if it was perfect. I validate everything now.