Lost iPhone

My iPhone was stolen so I marked it as erased. I can still track it because on Find My is shows up as erase pending but I called and they said that means it's completely erased. I just now got an email saying activation lock was requesting my password on my phone. But since the one stolen and the new one I got are under the same name, I don't know which one is requesting my passcode. If it is the stolen one that I erased, how can I ensure that they can't get my passcode? Do I just ignore the email?