hiding twin???

i was 5w4d and got told there was two sacs one is hiding halfway behind the other. i just had an ultrasound today and im 9 w2d and was told only one i saw something weird and asked and they said its a shadow but it never went away no matter how they turned it. Also i have not yet heard the heartbeat they did it on ultrasound but just measured.

please tell me what you think. i showed my aunt and her friend had twins without knowing till labor and said her ultrasounds was the same way. what do you think ? anyone with experience of a hiding twin?