Gabe Hamlin has been banned for two years after failing to prove he only got cocaine in his system by kissing a woman.
The 23-year-old prop, who was playing for Wigan before testing positive last February, said he met the woman on a dating site.
A report from UK Anti-Doping said: "Mr Hamlin indicates that he and the woman kissed during the course of the evening.
"Mr Hamlin maintains he did not consume cocaine or see the woman consuming it; he suggests that she visited the bathroom several times' and that he discovered white powder in his bathroom the following morning."
UKAD said they "did not accept" the version of events, but said that "on the balance of probabilities" his use of cocaine was not intended to be performance-enhancing.
Hamlin was suspended by the RFL last April and immediately flew home to Australia.
Pat Myhill, UKAD director of operations, said: "Cocaine is a dangerous drug with significant health risks, which has no place in sport.
"This case is another example of a metabolite of cocaine resulting in an athlete receiving a ban from sport.
"We realise that the length of sanctions for this substance can vary between cases, this is because of the specific sanctions laid out in the Anti-Doping Rules.
"The independent expert witness in this case ruled out the possibility that ingestion took place during the in-competition period. This means that a possible four-year ban was reduced to two years.
"Athletes are solely responsible for what is in their system, regardless of how they claim it got there and whether there was an intention to cheat or not. It is quite simply not worth the risk."
