Ignore Winch people, he/she too is high....on ignorance!!!
This is a very common error when it comes to drug testing. It must also be remembered that a lot of prescribed drugs contain ingredients which are otherwise illegal but once they are controlled they are more then safe. Drug tests will pick up everything and therefore will show up. The pharmacist letter should be all you need however if it is not, then you could have a very good case for a lawyer!!! LOL!