I have had this problem several times, only after loading saved files. There was one file in particular, where the textures on the hip would always disappear on loading. No big deal to reapply the texture tho. Then, there was another file where the hip itself disappeared from the figure (and it was not just hidden from view). I wish I knew an easy fix, but I had to replace the figure in the scene, and usually ended up remapping and reapplying some props.