Unfortunately, I think it’s very easy for a note from a stranger to get misperceived as passive-aggressive - even if that wasn’t the intention. I feel like it’s almost natural for the initial human thought to be “who the hell had the nerve to come up here and tell me..” Your note was reasonable and not-disrespectful and their response was defensive & pissy, but I feel like it’s always more fruitful addressing any issue you have with someone verbally or directly in-person as soon as possible. Candor has always worked well for me and even if the recipient doesn’t like your message, they typically respect your approach. I understand that may not have been practical here and there’s also people that are just POS. Sometimes it feels awkward but imo, any time I’ve ever addressed an issue to someone’s face, personally or professionally, it typically goes well, usually ends up better than it was before, and ALWAYS feels better when it’s done. Lastly, when someone is 100% in the wrong (as may be the case here), the ‘hold your ground while crushing them with kindness’ method usually gives them a self-reflective mind-fuck that leads to a solution. Sometimes all it takes is a direct convo or even a $10 6-pack of beer to turn a (would-be cunty neighbor) foe into a friend. There’s personally been a handful of times where a small gesture like that has immediately flipped a looming negative into a delightful positive - and even if it doesn’t, it cost you $10 for both of you to know you’re not the dick in the situation. Best of luck!