When did I become invisible?

Do you ever wonder if you're invisible?

Like when you're in the grocery store. And you've conscientiously pulled your cart to one side of the aisle so other people can pass while you scan the shelves looking for oh, let's say a bottle of basalmic vinager. And along comes some woman who doesn't make eye contact. With anyone. And stops her cart. Right. In front. Of you. Blocking your line of vision to the shelf of vinegar. And still. She won't make eye contact with you. Maybe it's because you are invisible.