Very sorry to hear, Anazor. I agree with horseydog. It's definitely worth going for second opinion to be certain of the diagnosis.
I did hear of an acquaintance who waited a week after no heart rate detection at 6-week point, and fetal heart rate was detected at subsequent scan.
To share, my husband and I decided to terminate our first pregnancy early 2016 after we sought two opinions and both confirmed no fetal growth over a week with very slow heart rate. There's high likelihood of natural miscarriage in due course, possible developmental complications etc. We chose to go for D&C over natural miscarriage as we preferred the abortion to be done professionally in a medical healthcare environment, and we could schedule the surgery date (my husband could be with me) and recovery period... instead of waiting for natural miscarriage which may happen anytime anywhere. From an emotional front, it also meant the situation was dealt with decisively, we could recuperate and move on sooner to try for another.
HUG.