You can not be terminated. But since it's your last day of sick leave and you feel OK , just go in, make nice, but let them know of the error. It will actually work out to your benefit.
Do you have a doctor's note saying when you're allowed to return to work? If it has a specific date on it saying when you can return to work, then you can't return to work until after that date.
You should have gotten something in the mail from kroger that said from what dates your medical leave begins and ends. Go by that, if you need more time bring in a doctors note to the store you work at.