Maybe the sign wasn’t large enough?

In his defense, eyes are hard to use.

When dealing with the Shopper, always keep in mind how poor his visual acumen is. Often they have remarkable difficulty viewing things that are directly in front of them. Curiously, they also have difficulty viewing things at a distance, the poor wretches. This leads them to ask incredibly stupid questions, much to the dismay of anyone nearby with a working brain. Approach them with great care for they are delicate creatures whose egos can be bruised easily.

-The Retail Explorer