Ultrasound tech said something different than doc

I’m going to be 6 weeks tomorrow and we had a scare today where I started cramping and bleeding and I assumed I was miscarrying again but we went to a scan to check and it turns out I just have a small hemorrhage by the baby. Question is: ultrasound tech said she could see the baby and could even see the beginning of a heart beat but the doctor said she could only see the yolk sac. Has this happened to anyone else or does anyone have experience reading these and can interpret? Thanks in advance !