Straight possession not likely as the courts are way to full of idiots out there to worry about one dude who admitted somewhere doing dope.
To answer your question though yes: A criminal conspiracy in a major drug deal - you can go down for conspiracy even though no drugs were found on you
Another scenario I am aware of: a long time violent criminal admitted under questioning to an investigator to being on scene of a shooting. He stated that while he did not shoot the victim, he "pulled out" his own gun and shot back at the parties involved. No gun was found on him, but based on his statement during questioning, he was tried and convicted of being a felon in possession of a firearm. A very dangerous criminal was put behind bars for a while
If they used the drugs and the officer can tell they are impaired by it the person could possibly be charged.
They would charged with something else though.