Hogies you mention she cost so many dollars which suggests you're in the US or Canada??
There are lots of reasons this happened to your sow, were there any signs of her labouring to expel the piglets? piglets can also die in the womb and cause blood poisoning? also did she have access to anything she might have eaten that was poisonous as the classic symptoms of poisoning are as you describe.
A post mortem would have been your best option as it might stop it happeneing to your new sow if its something thats caused it is in your current environment.
I hope you have better success with your girl in January and i'm sure this happening will make you more vigilant for the signs of farrowing.
try this link which will give you some tips
http://oldspots.org.uk/getting_started4.aspbest of luck
Mandy