The cloth dynamics are saved in a separate file, with a name like "DocumentName_Sim_1_ClothName.dyn". As you can see, Poser derives the name from the name of your PZ3, the simulation name, and the name of the cloth item. If you move the PZ3 and not the DYN file, or if you rename it, the two will lose their association and you'll have to recalculate.