Confused help

Heya girls i had a miscarriag at 6 weeks on the 18th of October, no sign of period since then, i opted to stay at home during this time as i was so early and it wasn't my first so i knew what to expect. But as i said iv had no period since. Doctors confired miscarriage. Iv been very irritated and grumpy amd extra hungry.. so i decided to take a test which was very postive. Did this ever happen to anyone. My gp said it could have been vanishing twin syndrome but as i miscarried a month ago they probably wouldnt be able to tell me if it was exactly that. Could the doctors have missed a second fetus on the scan as i was only 5-6 weeks when i miscarried