Vehicle Start outside of vehicle

[rat55chevy]

I was at the dealership yesterday (oil, rotation, wipers..). The write-up guy went over to my truck for what I assumed to be VIN and mileage. Granted I couldn't see everything he did......He opened the drivers side door and start pushing buttons on the steering wheel. The horn honked and he hit the start button and the truck started. Say WHAT? He didn't have the remote, I could see it laying on the hood (where the porter put it when he moved the truck forward).

What did he do? How did he do that? Super secret de-coder ring?