They don't d&c the uterus for a tubal. The pregnancy is in the tubes. I have actually heard of it happening before.
Samething happened to my mom and my brother just turned 18. Happens more often then not. My brother had a twin. When it happened it terminated one baby but not the other. Don't know why.
Have they done an ultrasound or just a urine and blood test? I'm asking because if they did not do an ultrasound this could be a tubal pregnancy and that's why the D&C did not cause a miscarriage. Your daughter really needs that ultrasound, if she has not already have one. If she has, it sounds like they did not do a complete D&C before and she must have been pregnant before her tubal. It should have showed up on a test though before she had either of these procedures done. Of course it can take some women longer to get a positive when they're pregnant. If your daughter is 9 weeks she's actually only 7 weeks because they add two weeks.