Vanishing Triplet - Bleeding Question

Im 8 weeks pregnant with twins, yesterday I started bleeding heavily accompanied by cramps. We went to the hospital right away - the twins were fine and heartbeats strong but they saw a third sac behind the twins and said that baby never developed and Im basically having a miscarriage of that one. My dr reassured me that the twins would be ok and that I should just but my legs up for two days and rest. The problem is Im bleeding a lot... Heavy clotty blood. He said this would stop in a few days and that I could go in daily for a scan to check on the twins. 
Everything online says most women doesnt bleed with a vanishing 'twin'. Has anyone else had this? Were you bleeding and crampy and how long did it last?