Faubert was only included in the squad at the last minute after defender James Tomkins suffered a calf injury in the pre-match warm up. He had left Upton Park before the message could reach him he was now required to sit on the bench.
A West Ham insider told ESPNsoccernet on Monday: "He left the ground when he was not picked as a sub - pathetic really. We are in the process of trying to find out what went on."
Faubert left the ground in the belief that he was not needed and, although the club managed to contact him some ten minutes after the kick-off, he then refused to return. It is understood he may have left the ground because he had had some time off as one of his children was ill.
West Ham were forced to name only six substitutes instead of the permitted seven.