i'm sorry to hear about your scan. i had a similar thing happen at my 12 week scan, after i had seen the baby and heart beat at 6 weeks. when i had my 12 week scan she could see the sac but not a baby. she did an internal and did manage to find the baby, which was tiny and hardly visible at all.
sorry it's not what you wanted to hear but that is my experience. wishing you all the best.