He could be taking a masking agent. He could be doing a ton of things. We only have his word to go off of because the NFL will never admit what he took. They dont speak on that matter EVER.
As silly as the drug testing might be, the rules are rules, and when you are in the NFL you should be "paranoid" to know what you are taking. They arent left in the dark on these issues. I'm sure they could call any number of people and get it cleared up fairly easy before he takes it. It certainly would be quicker than the 4 game suspension he could be looking at unless something magical changes before its handed down.