Given his length of service he must have been tested umpteen times
Perhaps this explains his choice of drug. I remember hearing some years back that, while marijuana would show up in urine tests for weeks after the event, cocaine taken on a Friday or Saturday would have vanished from the system by Monday morning. In fact, this revelation appeared after a techie at a flying station apparently wrote an open letter to the command chain to point out that CDT was useless at detecting anything other than hash, and that some of his peers were in the habit of using cocaine, safe in the knowledge that they were very unlikely to get caught.
Please note I am not condoning any form of drug use by any serving personnel. The way that the current case has been reported makes it sound like either breathtaking arrogance or a cry for help by the individual involved.