Hi Joe, and welcome to the Sphere.
So, I had a quick Google. Here's a version of Mitchell's poem with the sweetshop line that was posted on an online forum in May 2006, 2 years prior to John's post; you can find it toward the bottom of this page:
http://vancouverjazz.com/forums/arch...hp/t-1643.html
Is that the one?
best,
Matt