Bakary Kone's sixth-minute strike settled Garde's final match in charge, but the coach and his assistant Gerald Baticle were pulled up on their treatment of the referee.
At a disciplinary meeting on Thursday, Garde was served with a two-match ban with one of those suspended, while Baticle, who remains at the club following his former boss's departure, serves a one-game suspension.
Hubert Fournier took over at the Stade de Gerland last month after Garde announced that he would not be renewing his contract in order to take a break from football.
Lyon achieved a fifth-place finish in Ligue 1 last season, securing a UEFA Europa League berth by just a single point.
The season represented the worst finish under Garde during his three years at the helm.