Just to be devil's advocate here, I try not to automatically assume the worst in people. I say that and also add that you should always be alert and aware of your surroundings and trust your gut feeling. Looking at this particular situation from the outside, I wouldn't discount the possibility that this guy was just simply fascinated by you and trying to get closer look. Someone that wishes to do you harm would not typically approach you inside a store and say something to you. A true scumbag would probably be a little better at being discrete and not give away his presence until he was able to suprise you in the parking lot. The whole thing with the cell phone up to his ear was him trying to get a good picture of you without being obvious and the "doing something else on his cell phone" while he was walking out to the parking lot was him checking out the fruits of his labor. Still creepy? Yes. Where you right in trying to evade and distance yourself? Certainly.
Just my $.02, if it's even worth that.
Kim