He had been due to make his first start of the season against the Diamonds.
Anderson, who joined the club 13 months ago from Bristol Rovers, will argue that a drink had been spiked.
Swansea chairman Huw Jenkins told the South Wales Evening Post: "Ijah Anderson tested positive for recreational drugs last month and was suspended by the club with immediate effect.
"Ijah is innocent until proven guilty and we are still waiting for the final outcome of the FAW hearing.
"But, obviously, if it does turn out that he has used drugs our policy will be one of zero tolerance and he will be finished with this club."