Working Dogs(Police Dogs) are trained specifically for Drugs ie: Pot, cocaine, heroin etc., some working dogs are trained specifically for scents such as a piece of someones clothing ie blood hounds. Blood hounds are used to find trails such as a prisoner has escaped from prison, or a lost child. Some working dogs are trained specifically for cadabers, such as after 911 to look for bodies alive or dead. Labrador Retrivers are usually used for explosives. I have never heard of a working dog being trained to find AAS. Maybe the drugs were found because the clothing had a smell on it that the dog is trained for such as pot or maybe the shirt had some cologone on it that intrigued the dogs scenses, or the shirt was worn during the 4th of July and had a powder residue smell on it.