I found it in the back of my truck later that day. It fit together in this interresting way! The uprights slip over a bridle joint in the base pieces. It's about 6 feet tall and 5 feet wide.
Here is my prototype of the system, about 3 feet by 3 feet. It's made out of old scrap pine from a house trim replacement job, old doors, and an old oak futon frame. The shelves are a variety of widths just to experiment with form, utility, and proportion.
The design really grabbed my interest. Next iteration will be made of hardwood and incorporate some changes suggested by folks who have seen it. This mock-up is made of trash wood, 100 year old trimwood, old fir doors, and a futon frame I found two days prior to getting this crazy idea!
Here's the joint detail....