Just to offer another option, that no-one has forgotten since could be down to the deterrent effect from the harsh punitive measures taken couldn't it? Maybe footballers are one of the few groups who respond to harsh punishments as a deterrent.
However he may also be thick and lying, I don't think it has to be an either/or situation for him.
We'll never know I suppose, but he must have known the repurcussions, players will have the importance of drug testing explained to them, to 'forget' is a bit strange, when I imagine the club employ certain people to remind players of such important things, but that's total speculation.
Either way I don't feel as though he's the right man based on other things too. Also, seems a strange time to give it to him when this is the worst period he's had in his career, he's hardly been playing and when he does his body language and actions (the ban) make him seem like he's developed a bad attitude