Oh Sylvia, I am sorry to hear about the two little ones.
It sounds as though mum has got them snuggled up warm now - my Meg did the same, there'd be a beehive of straw in the corner, and deep within it, there they'd be, snug and warm. I was glad I had put plenty of straw in there, even though some folks warn about having too much straw and the mother not seeing a piglet she's about to lie on! But it seems that OSB sows do snuffle about pretty thoroughly before lying down, and in the absence of a heat source the straw beehive is needed to keep the babies warm while mum is outside.
I did have on standby ready in case needed (I think I have just said the same thing three times, sorry) a hot water bottle. With only 5 piglets and plenty of straw in September Meg managed fine, but if she was farrowing now I think hotties would probably be useful. Just a thought.
Most likely, as others have said, Mrs C knew something, and has kept the healthy viable ones warm. Let's hope so and that she can now rear these. Best of luck!