Your thread needs more clarification. Your title was no fetal cardiac activity;so that goes to say there was a gestational sac found in the ultra sound?. but your details inside goes to say that there was no IUP, nor ectopic pregnancy. this rules out the title of 'no fetal cardiac activity', while there is no documented gestational sac visualized. SO, no ultrasound sign of gestation there. With this scenario, I would go for nongestational ultasound- transvaginal, trans abdominal, whatever was performed.
Just a qualitative pregnancy test alone cannot confirm pregnancy. Even some beta HCG results can go for false positive tests for pregnancy ,for eg, trophoplastic diseases which are considered to be non gestational.
So ultra sound obstetrical have to have some ground to place them in obstetrical US.
This may need beta HCG test and another repeat US after a week or so to consider to place for obstetrical US
Does this post (my response) make some sense?