If they did a "forensic examination" that means dogs and swabs. And if that didn't pick up anything, then he should probably try and get his money back.
I remember I bought a bag of what I thought was E and munched my way through 20 of them at a weekend rave. My internal organs started shutting down on the sunday morning and the next thing I woke up in hospital a couple days later. The doctor was like "It was mostly amphetamine, if it had been pure E it would have killed you a lot sooner, how do you feel" and the first thing I said was "ripped off". That's when I realised I had a drug problem.