Every big retail store has security lights. The place would not have been completely dark. And in most such places, the regular lights, at least in areas, can be turned on the same way your home lights can: with a wall switch.
caw
The security lights in stores around here can be a little pathetic. And sometimes they hide the overhead light switches in weird places that wouldn't be easy to find in the dark; apparently, they don't like customers flicking them on and off. (Er, or so I've heard... somewhere...)
Some places lock their bathrooms at night, too. That would be an inconvenience, to say the least.