Asking my boss for my paycheck

Ta
I work as a nanny. I watch a 5 month old 8 hours a day, 4 days a week. I get paid every two weeks. I was supposed to get paid this Monday but nothing ever happened. I've been working for her for a few months and she has never forgotten before. I get paid in checks and she usually puts them on her fridge. How do I ask her politely for my pay check? She is very nice and I don't think she purposefully isn't giving me my check so I don't want to offend her