Johnn,
Wait until you actually hear that they have disqualified you before you give up.  The post-test interview you described may have been the examiner’s attempt to get you to “confess” to drug use.  

Just because the examiner said you showed a significant reaction on the questions about drug use doesn’t mean that you did.  A very common tactic is to claim you showed a reaction to see if you will confess, now that you have ostensibly been “caught” by the machine.  That's the whole reason behind the trick at the beginning of the test where you are directed to lie - so that you will believe the machine can "catch" you if you don't tell the truth.

Since you didn’t confess anything the examiner may report that you passed.  Try to be patient and don't give up.