Even if what they were measuring was estrogen, they would not be able to tell by estrogen levels that a pregnancy
had failed in
just 2 days between tests. Estrogen
might go up pretty soon after implantation (not conception) and it might go down after a pregnancy fails, but it would sort of drift up and down. They would be watching your hCG levels, not your estrogen levels, for this particular information and only from an hCG test would they get such a quick answer.