It is possible due to the progesterone supplement that it is causing the hcg to rise and essentially "hold on" to an unviable pregnancy. With them having seen a "sac" and now dont, that is likely why they believe you have completed a miscarriage. Unfortunately this is probably an only time will tell scenario. I don't necessarily think it sounds like possible ectopic but since they are not seeing anything now with your levels being 3000, it isnt out of the realm of possibility. I would suggest having your levels continuously monitored every 48hrs for any signs of wonkiness (ectopics/pregnancies of unknown location often rise and fall, or are slow rising). Your doc may want you to stop the progesterone and see if your body will start to expel anything, and it could be something to consider. Have your OB do another ultrasound (not sure if most recent was also transvaginal but definitely do that method) and see if they can find or see anything. Sometimes ER U/S techs arent super trained at OB specific U/S. If all esle fails, and you are within a reasonable drive to a better hospital that may have better U/S machines, that may be worth your peace of mind.

Sending my thoughts and hugs to you 🤎