Ultrasound scan

Did any of you see the yolk sac at 5 weeks by an abdominal scan, I went to a private clinic in the uk for an early ultrasound but they’re not licensed to do vaginal scans so it had to be done abdominally, all that was visible was the gestational sac and now I’m worrying as to why the yolk sac can’t be seen, the sonographer started talking about miscarriage and told me to take a pregnancy test but if the gestational sac is there why would I need to do another test?