First of all - if you haven't already, I would call your doctor and get in for an ultrasound immediately.
I had two grade 1 embryos put back on 4/4/06. My HCG levels were very high in the beginning - and there was speculation that I could have been having twins. At 6 1/2 weeks - I had bright red bleeding with two clots. I had no cramps, however. The entire episode lasted maybe and hour or two.
I went in the next day and had an emergency ultrasound and saw that I was carrying one healthy baby. I am now 11 weeks and everything is still great.
Since I had no ultrasound prior to the bleeding episode - I will never know if I had twins. Still - vanishing twin has been suggested.
To answer your question - yes it is very possible that you miscarried the one and are still carrying a healthy baby. Bleeding is very, very common in early pregnancy - although it is still scary. I think if you were miscarrying the whole pregnancy - you would have been bleeding a lot more. I am not a doctor - I am just telling you what I know from my experience and my research.
Good luck - I hope everything is okay
