Yes, sudden oak is a pretty serious thing. It is killing off a lot of trees in my neighborhood. As far as I know it doesnt affect orchids, the reason they wont ship it is to try and contain the disease and not spread it all over the country.

As far as buying fir bark from a pet store, Jmoney hit it on the head. You really want no wood in it, so I suppose you could get it and pick out the wood, but if there is a ton in there I would imagine it would not be worth it. I would wager a guess that there isnt the same quality standards for pet bark as there is for orchid bark.