I Just Had A 20-week Anomaly Scan (single Foetus). Unfortunately

I just had a 20-week anomaly scan (single foetus). Unfortunately baby was lying with face down position and the scanning doctor was unable to view the heart and organs properly. She advised me to come after 2 days stating that it is unlikely that the foetus will change its position much until 1-2 days. Also, said that due to my thick abdominal wall, poor penetration of waves. Is it correct that foetus will actually not change position much for 1-2 days? Isn't this that time of pregnancy when foetal movements are actually start to be felt?