When you select the save and close button in the simulation it saves where you are and closes the simulation for you to return at a later time to the same screen. Please note that it does not save any answers that you have not submitted on the current screen i.e. any text answers on that screen will be lost.
If you have entered text answers that are not complete you should copy and paste them into a Word document before you close the simulation. You can then copy and paste them back into the simulation when you return. As noted in the Simulation Player Guide and Tips section of the Knowledge Base we recommend formulating your answers in Word and then copying and pasting them into the simulation.