Oh i am sorry!
These things do happen though and orphans can be an uphill struggle but worth it when it goes right. Don't get too disheartened, sheep do this to you sometimes.
We used to do a lot of orphans at one time but now with so many sheep about i find i just don't have the time so we tend to pass ours on to people who do.
I have to say i've had really good strong orphans doing well and i've found them dead in the pen but it's usually always been when the gut flora balance isn't right around the time of weaning off milk. The train of thought is the gas in the stomach expands and presses on the heart causing it to fail.
Some farmers say the milk should be watered down and you wean them off gradually others say cut the milk right out once they are eating creep/solids wel,l so it's a bit of a minefield.
the last time i did some was 2 years ago and i cut the milk out at 5 weeks old they bleated a bit but soon got over it but you do need them to eating solids well for this to happen.
Good luck and don't give up!