First of all, saying that I wasn't very nice is a huge overstatement. These friends barely spoke English. They required me to give my ID without giving reasons for doing so. I read that you did have a flatmate and you *voluntarily* agreed to rent an empty apartment. Please do not complain about your own choices, because I would have rented a different apartment if that was a rule you have chosen to stick to. I've rented places on AirBnB multiple times before and had only good interactions and left all apartments clean and flawlessly untouched. I recommend thinking twice before saying that someone isn't nice just because they aren't willing to give out their personal data without a reason.