It never fails. As soon as you get to where you are going the preschool set needs to use the facilities. Doesn't matter if you've gone ten miles or ten feet, nature's call has a strong desire to see the decor and smell the handsoaps.
If the place has anything interesting at all -- an automatic hand dryer for instance -- you are destined to make multiple trips to the lav during the course of your shopping experience.
Potty training does have it's price after all. You might as well put the savings you gain from skipping the diapers aisle directly into the unnecessary things you will buy so as not to look like a schnorrer whenever your kid needs to use the washroom at a store that doesn't legally have to provide them to patrons.
"Oh, mama. Can you pick me up? I can't reach the sink. Look! The walls are purple. And they have that blowdryer thing on the wall. I want to push it again ... and again ... and again. Just one more time? Pleeeeeeeeeeeese oh Plaaaaaaaahhhhhhzzzzzz."