Question: Was told today that they think it's a girl but aren't 100% sure

They saw the three little lines, but the Baby wouldn't open their legs and show us what's down there. She said she thinks it's a girl because she saw the three little lines that indicate that it's a baby girl, but to not start buying pink stuff because she could be wrong. Has anyone ever been told they think it's a girl and then find out at their anatomy scan that they're having a boy. This is my first and I'm really wanting to have a boy before I have a girl, obviously I am going to love this baby no matter what they are. Just want to hold out hope of a boy is all haha.