I reckon you should write in black marker across the note "I know where you live" and slip it back under the door.
or what about
"I am sorry, I did not realise it was private property. It is always a challenge to find a parking space for bikes. I will be more careful in future. Sorry for the inconvenience".
or what about
"I am sorry, I did not realise it was private property. It is always a challenge to find a parking space for bikes. I will be more careful in future. Sorry for the inconvenience".