Yep, colostrum is the first milk.
And thats what we figured as well, that he had already nursed on the Doe, otherwise he might not have lived.
You might remember how in last month me and my my friend, we tried to keep newborn lamb alive after we found it under hypothermic condition from barn corner. (I was visiting my friend's farm)
The eve was first-timer in birthgiving and didn't know how to encourage the lamb to nurse milk from her, so the lamb was missing important dose of colostrum and we had to borrow frost cow colostrum from neighbor farm, melt it in micro and to feed the lamb with doser (after we had brought it indoors - the barn floor was too cold to keep the lamb's body temperature up).
But the operation failed. Lamb puked up all the milk we got her to swallow with doser and she died couple of hours later. We found her too late in the first place, too many hours from birth.
But now we are more wise. If another similar situation comes we bring the lamb indoors first, then start to feed him/her. Not try to keep lamb's bodytemper up in barn with air heater or warming lamp.