Ahsanu Allahu ilaykum. I accidentally scratched a parked car and tried multiple times to rectify it. My non-Muslim family forcefully opposed me. I still left a note with money/details, but while going back home (I wasn’t driving) I saw them remove it. I cannot return. What is my obligation?

It's upon them, not upon you. You put everything out and left, and then they told you they removed it or something like that. But if they went and removed it, maybe you could have waited for them to go, and once they left, you could have gone back and put another note. I do not know how the situation is. However, all in all, the transgression is on them, not on you.