Just letting you all know that I had my first Muscovy hatch of the year. It was the first nest for my little black hen, and she abandoned it about 5 days before they were due to hatch. They sat for three days and were extremely cold. I figured there was no chance for them, and I did an autopsy on one of them... and it was dead. The next one was alive! So, I put the rest of them under another broody hen, and all hatched! I couldnt believe it.
Moral of this story: Don't give up on them. Three days in 50 deg weather and they survived.