The freezing temperature would not have hurt it.
The important thing to know is was it still plugged in all night.
If it was, it is most likely toast as it has surely been discharged below the minimum limit.
If you put it on a charger it will most likely error out.
Just found this on a website:
[h=3]How does cold weather affect my LiPo battery?[/h]Like most batteries, the temperature of a Li-Po has an impact on its performance. Consider that batteries rely on a chemical reaction in order to provide a current – a low temperature reduces the speed of this reaction and a reduction in overall pack performance may be observed on a cold day. Allowing a Li-Po pack to freeze is certainly not recommended, as this would almost certainly damage the pack.
I'd plug it into the charger and see what happens. It may not charge at all if it is below 9v. With a programmable charger you can sometimes revive a LiPo by charging it as a NiCad until it is above 9v. Keep a close eye on it if it does seem to be charging.