Im sorry about your lamb

I couldnt have seen this post due to me going to bed early and working with animals from waking up this morning

I am replying because I had a lamb that sounds identical to what yours sounded like, except that it survived! I was so so sure it would die and didnt know what to do, in the end I used my cure-all (ground ginger and codliver oil), pumped it full, shoved a doggie fleece on it
http://www.equafleece.co.uk/store/dog_jumpers.html and put him in the field to pass away.
The next morning he was slightly better, and he has steadily improved from that moment, right now he is fine but he is tiny! he weighs 17 kilo compared to the others of 30 kilo, but he isnt thin, just tiny.
The only thing I could think of, was when lambing one year had the same but the lamb died, and we cut him open (sorry guys) and he had a deformed Epiglottis, which as far as we could make out, when he was young it didnt bother him so much because of the food being mainly milk (liquids) but as he got older (around 8 weeks) food he swallowed must have gone into his airways gradually and although not enough to hamper his breathing, it slowly became infected and he got thinner and weaker over 2 days, until he could no longer stand and he died.
I have no idea if your lamb could be this, but I know it can happen and I am sure my one little lamb has a similair problem as when he eats long grass sometimes, it causes him to cough and splutter it up again. But I think his is no where near like what the lamb that passed away's deformation was like.