By law in the USA, one must be notified if they are recieving a drug test.

Doctors wouldn't waste their time drug testing patients, because:

A: It costs more money
B: Time consuming
C: Unless you're having psych or lung problems, they don't know, or really care.

Docs can't release patient information without a signed consent. Those places they send you to get piss tested? Those are minimum wage "technicians" who have VERY little to no medical training.

Don't worry about it.