They can test drugs pretty quickly these days - enough to know if something is rock salt or not, anyway. Himalayan salt is literally marketing speak for rock salt. NaCl. A pill testing kit will tell you if there's any one of tons of illegal substances in something within seconds. The idea of a Chinese supplier "accidentally" sending Methylone instead of Himalayan Salt or whatever is quite laughable, due to the a) differences in risk and b) differences in price. It's like me accidentally sending someone gold bars instead of copper coins.
Your friend is now running away from the police, publishing blog posts about what's going on and trying to get media coverage, etc.. Describing the DEA as a "criminal gang" on the blog and who knows what else isn't exactly going to help his defense, either.
There's something really dodgy about this story. If it was rock salt, why wouldn't you just hand yourself in, explain what it was, and let them do their tests? If I was pulled over and arrested for cocaine possession and all I had was a bag of sugar, I wouldn't run away from the police, because I'm not an idiot. I'd wait until it was all cleared up, THEN write a blog post about my ordeal and the ridiculousness of our drug laws.
Your friend was trying to import large quantities of scheduled substances and got caught.