The Frenchman faces a disciplinary hearing and a possible £65,000 fine for going home before the 1-0 defeat to Birmingham.
Faubert had left Upton Park when he was called up because of a late injury to James Tomkins.
The full-back, 27, insists he needed to look after his elder son as his wife had taken his baby son to hospital.
But Hammers chief Grant revealed: "I said to Julien what I think and the other players know that. It's an internal matter."