Possible twin?

Can anyone make sense of this...

I went in today to confirm miscarriage. Back story: there was no heart beat at the last ultrasound, yolk sac was abnormally large, and my hcg levels were dropping from 86,000 to 50,000.

At today's ultrasound my dr confirmed still no heartbeat and baby bad not grown at all. I was measuring 6w3d last week and was still measuring 6w3d today. However she pointed out on the screen a second yolk sac within the same gestational sac that we had not seen there last week. She confirmed there was 1 fetal pole, baby with no heartbeat, yolk sac, and what seemed to be another yolk sac.

My dr said she couldn't confirm if it was another yolk sac, but she couldn't confirm it wasn't either. She just said it looked like the start of a possible twin. But why so late? Is it a vanishing twin and I just happened to lose the other as well? I'm so confused. Can anyone help me understand this?? And if it isn't a twin, then what did we see?