Actually it was revealed in the previous post, but I'm not sure the revelation was very telling. The mystery item I made, was, in fact, a mushrooming bag! As of writing this post it has not actually gotten any use, despite the fact that I found this swell fellow growing in Julie's garden.
Unfortunately I don't actually know what kind of mushroom this is, so I am just going to go ahead and assume he is not of the edible variety, for my own safety.
I learned about the importance of mushrooming bags from the book Animal, Vegetable, Miracle. The idea is that once you pick a mushroom, it is still dropping all of its spores, so if you want those spores to hit the earth and have potential to become new mushrooms, it is best to use a mesh bag to carry your harvest.