Frustrated cats don't always vent right away, they may seem calm at the moment but I bet you, a territorial kitty never forgets, the complaint call just comes delayed. It can be weeks or even month after getting aggravated over something, but when the shit hits her fan, she'll let you know.
Unlike cat pee, locating the crime scene can be challenging and boy!, they can be so incredibly creative when it comes to choosing the "purrfect" spot for the message - often just a few little drops which makes it so darn difficult to find.
Eventually I figured it out: water and simple anti-bacterial hand soap works best and gives quick and lasting results. A little spritz of feline facial hormone spray applied to critical spots, and natural flower essences added to food or drinking water, and life with kitty has become much more pleasant.
That is of course ... until kitty's hotline rings again and it's time for a talk.