Some jerk has probably hidden the other one waiting for a sale. Go back and hide the one that is still there to teach him a lesson.
I did go back the next day - no sign of the shoe, goddammit!
I also had to try on that Bailey & Weatherill suit. How often will I get a suit made by a respected and departed English tailoring house, especially in the '60s rock star style that I love so much? Alas, the pants were WAY too tight for me. Any skinny guys interested can ping me, and I'll pick it up if it's still there the next time I'm in.