I can guarantee you that most comes out every time. It might not come out immediately but seep out over the next day. There is really no other place for it to go. What you ejaculate is semen that contains a lot of fluid and a microscopic amount of sperm. Some of the sperm will go into her uterus but the rest of the semen comes back out.

The reason why it is a lot if you have not done it in a while is because you are ejaculating a lot more then. You will see that when you masturbate as well.