What Does Austrian Theory Say About Hyperinflation?

Erm, not sure I agree with you there. See the following:
https://forum.freecapitalists.org/t/recessions-are-deflationary-by-nature/895/3

I think this is a common myth that many people learn in economics classes at school… that never seem to cease repeating the mantra that “recessions are deflationary” just because the Great Depression was. But the Great Depression was also accompanied by monetary contraction.

As Friedman says, inflation is always and everywhere a monetary phenomenon. Whether money is being created or destroyed in a recession will depend on a number of factors. Certainly production will be hit, but will the quantity of reserves in the banking system decrease more than production does? If the answer is yes, then you’ll get deflation - if the reserves hold out better than production or even increase, for example because the central bank keeps on a printing, then you’ll see inflation. Another thing that might cause inflation is if USD reserves that are presently held in foreign banks come back to the US.