Very neat. I was hoping to unintrusively tinker with my buzzer in my condo, but I found that the wires coming out of the back of the device used some sort of signaling system, and I couldn't just use my own controller to switch on the door buzzer to let someone in from my phone.
I would suggest complaining to your local branch. You basically have proof that there was no genuine attempt at delivery. The driver will get in trouble.