Around these parts (and most of the parts where I've been), we tend to be more "pro-active" about dealing with this situation--a client would not have set for three hours waiting for a scofflaw to move their car.

Most places, business or residential, who have private parking areas routinely tow vehicles that are unauthorized or improperly parked. Often, there is a sign displaying the tow service number, for those who need to recover their vehicles. Before that occurred, someone likely would have run into all the adjacent offices seeking the car owner, and often concerned parties or even bystanders might improvise a way of moving the car.

In a couple neighborhoods I've lived in, a tire iron would have been used, either on the offending car or it's driver. There were signs that said, "Don't Even Think About Parking Here" and they knew...

Chalk it up to cultural differences, I guess...