I have been scammed a couple of times, but I have never lost a package that was actually sent by the vendor. I have a 100% delivery rate.
Every time I was scammed was the result of finalizing early. This is bypassing the escrow system and giving the vendor the money immediately. Usually new users are asked to do this, and some vendors require it. I've learned my lesson and never FE (finalize early) now.
You can find non psychoactive/psychiatric drugs, it just varies a lot and you need to keep your eyes open. Certainly the market for what you are looking for is smaller, but it is there if you are persistant about it.