Actually as I stated above, it's not impossible at all. And if they were doing an ultrasound for IBS they were doing it over her stomach and intestine, not uterus, so it's entirely possible they missed it.

literal people are scary, man, literal people scare me
out there trying to rid the world of its poetry while getting it wrong fundamentally down at the church of "look,it sez right here, see!" Ani Difranco