I had one once in my living room. I was pissed. The host told me it had written about it in the description. Sure enough it was there when I looked carefully. Still what the heck. In a Boston Airbnb with my parents visiting from abroad. I ended up leaving a one star review, and he begged for me to take it down. I explained long and large how wrong what he did was and left my one star review. Felt good.
I had this happen in Seoul, the host messages me and asked me to not leave the AC on when I went out (it was a 10-minute walk down to the corner store) - I was a little confused how they knew I'd left it on, so I purposefully left it on and went out, sure enough I got a message as soon as I left. I messaged back and said it wasn't on, and they said they had a camera and could see it's on. I contacted Airbnb and they moved me to a hotel that day, but I wasn't super stoked.