Saido Berahino was suspended after failing a drugs test in September, Sportsmail can reveal.
The controversial England Under 21 striker is understood to have tested positive for a recreational drug in an out-of-competition test.
The suspension ended before he completed his £12million move from West Bromwich Albion to Stoke City last month.
Stoke, the FA and Berahino's agent declined to comment, with a spokesman for Stoke simply requesting that this newspaper contact the governing body.