Hey hey, I'm in vaguely similar predicament. One of my ewes gave birth to a single lamb (3.76kg) yesterday evening. I helped with the birth, but was OK.
However, I was very surprised to see only one lamb. I had a feel inside her, and could not feel a second lamb, but I might have missed it as I really don't know what I'm doing.
Worried that she has a second lamb which has died inside her, then not sure what would happen, would she pass it? Tried to have another look inside her this morning but she wasn't having it, and didn't want to push it? The ewe is eating and drinking and looking after the lamb, doesn't show any signs of distress. Any advice welcomed?