What is the chance of pregnancy in this situation?

I didn't cuum in this girl, but I probably did pre-cuum. I'm aware that precuum contains sperm. I had her take the morning after pill 30 hours after. If she was ovulating does the morning after pill not work at all? I have no idea if she was ovulating I am just worried. I have read some people saying that once fertilization has occurred the morning after pill can't stop the egg from implanting to the uterus. Is this true?