Here's a hint.

Suprisingly, despite having no bottom pulley I was able to complete the ride which included an additional 1 1/2 miles of singletrack and a few miles of pavement. The pin that holds the plates of the cage together acted as the pulley and it actually continued to shift really well. Thankfully, you can replace the lower cage and pulleys without replacing the whole derailleur because these suckers are too expensive to just throw away.