It probably was not on when the mechanic finished. Until the wheels start spinning, the light would not turn on.

As a mechanic a can say that when I finish with a vehicle I check the lights while its on the lift still I will quick glance while driving it out. when he drove the vx out its very possible the steering wheel covered the abs light so he didn't notice it. My steering wheel covers my abs light and turn signal indicators if I sit forward (which I always do while driving customer vehicles)