I have sold my phone

I sold my phone to someone and now I had it set up to erase once it went back online but it won’t.

I can see the phone on find my iPhone app. It said pending erase once it goes online but it doesn’t seem to work for the gentleman on the other side.

Why am I still finding it on my side as it is listed on my list as pending?

The screen was completely black so I had no way of setting the phone back to factory settings he was going to make a repair to it. I don’t really want to give them my Apple ID and password.