I was working on a sculpture, then I opened up a new polysphere to do the eyes, and my original sculpture disappeared from the tool palette. Is there any way to get it back?
I’m guessing that you used LightBox to open the PolySphere Project.
Projects effectively reinitialize ZBrush to the state that was saved by the Project. That is why when you have work in progress and go to open a Project (ZPR) file you are given a warning message asking if you want to save. Proceeding without saving will delete everything that is currently in progress.