That vendor's email is probably the most expensive email mistake ever made. I wonder if he sent it to the old Levandowsky (Google) email that his email system probably autopopulated?
Misdirected emails happen. I was even recently called by a vendor on my cell phone (side effect of open offices: no office phone) for an old company that wanted to talk about the sensors they were using for a new project. The vendor still thought I worked there even two years after leaving.