Did you and your employer part company on decent terms? If so, go to the office and ask HR to printout the SVP that is given at the time of the online cancellation of the S pass. It will have the exit date already on it.
If you are NOT on friendly terms with your ex employer, I'd go to MOM immediately and explain this to them as you must have that paper in hand because with which you are an illegal alien here.
SOME PEOPLE TRY TO TURN BACK THEIR ODOMETERS. NOT ME. I WANT PEOPLE TO KNOW WHY I LOOK THIS WAY. I'VE TRAVELED A LONG WAY, AND SOME OF THE ROADS WEREN'T PAVED. ~ Will Rogers