I am pretty sure that they must disclose they will screen for drugs. They may actually give you a chain of custody form for the sample. if they dont say anything or give you that form there may not be a drug screen. My buddy who had the physical and the screen left the substitute in his pants pocket with a heat pad taped to it. the doc left the room and let him fill the sample container in private. he grabbed the quick fix and filled the container. it was risky but he pulled it off.

goof luck bro!