He would have been part of the random pool subject to drug testing. Outside of the chance selection in that program, there was only one time per year where he would have been before the FAA, well an AME, who would interview him during his medical exam. The protocol includes looking for indicators, but it's certainly not fool proof. The best safety net for substance abusers is those around them. Reasonable suspicion can get the pilot tested. If those people know but fail to report, shame on them. The one news items said a relative knew what was going on and it appears they didn't report. Shameful, and sad.