If you mean that no one has ever been identified and busted through a technical attack on Tor or SR, or a statistical attack on the block chain, you'd be correct, but the idea that no SR vendor or user has ever been busted is ludicrous. There are published news articles linking people to SR. Vendors and buyers live in the real world, where packages can be intercepted. 20 grams of MDMA is not a trivial amount. That's 200 doses. I wouldn't say that OP has no reason to be worried. Never get complacent.