Roxann, I'm sorry about your mother and not being able to say good-bye to her.  I'm guessing, but do you and your father have a strained relationship and that's why he didn't tell you in time?

I am sure your mother knows you would have been there if you could, you'll always have her in your heart.  If there are some things in your relationship with her that are unresolved, you could talk with a therapist about it, to help you find some closure.  I know it's very upsetting when things like this happen and we're unprepared, but life doesn't always happen at our convenience, so we have to find other ways to deal with it.  I hope your sorrow will lessen soon.  I'm sure you will always miss her, but one day it won't hurt this badly.  Take care.