Dopaman: It is actually a pretty old technique. Most pseuohalides will mask a substance. Usually KSCN is used and then is only detectable by a physical general test which still cannot determine cocaine, but only the high probabilty of prior or present contact with residue of ANY number of illicit substances.
I will not bore everyone will all the details but others use potassium thiocyanate, and I suppose others. The key is the porportion, with as much as 60% of the masking substance being used (60:40, 60 being the mask and 40 being the target substance).
First detected in Germany in 1998, only in Amierca much later, and usually WAS shppied via a combination masked to look like shaving from bulk iron shipments.
So...Dogs are NOT infallible.