Pregnancy: After 35 Community

Just reading the posts and am encouraged by what I've read. I'm a 44 year old who is trying to conceive. At 42, surprisiingly I found out that I was pregnant. When I went for the first vaginal ultrasound, the Dr. said that she saw what she thought was the beginning of the fetal pole & yolk sac, so she asked that I come back in 2 weeks. I did, and at that visit was able to see the baby and the heartbeat. The Dr. estimated me to be 6 weeks and 4 days. My progesterone was a little low, 10.68, so she prescribed progesterone suppositories for me to take day\night. She sent me on, asking that I make the next appointment in 5 weeks -- so I did. During those weeks all seemed well. It wasn't until 4-5 days prior to my appointment that I went to the bathroom, wiped and saw a little brown blood. So, I called the OBG\YN Nurse and she asked me how far along was I and I told her that I would be 12 weeks that coming Sunday and that I had an appointment on that following Monday. She told me not to worry because it's common at the stage in pregnancy to see a little spotting.

Well, Monday came, appointment day. We were supposed to hear the baby's heartbeat. She put the doppler on my stomach, NOTHING. So we went into another room and done the vaginal ultrasound. She looked and looked, called in another Dr. they looked and looked but did NOT see the baby. The sac was there intact, appropriate size for the stage of pregnance that I was (12 weeks), but still no baby...

I telling this story to see what others think may have happened to the baby. Couldn't have been Blighted Ovum, as we saw the baby and the heartbeat at 6 weeks and 4 days. I don't understand it, what happened to my baby? Can the baby eject from the SAC without me knowing?????