Thank you all for the feed back.
It's possible, a very close friend of mine didn't find out she was having twins until she was 29 weeks lol lil one was hiding much further up than where the other one was!
It is extremely unlikely that at 9 weeks an ultrasonographer would miss a second embryo. If you could actually see, not just hear, in other words if you were having an ultrasound and not merely listening by doppler, you would have seen twins. At that point, they are moving around like little gymnasts or teddy bears, and the beating hearts are clearly visible.
my sil had twins and she didn't find out until like 25 weeks cuz the other baby always shadowed his twin hb and all so it is possible.
Its possible my very first apt was 12 weeks and they only heard one hb..my 16 week check up she wasn't sure if it was the same hb so i went to get us and showed two babies