Jimmy Walker has returned to West Ham after Colchester failed with an appeal to extend his loan.
The veteran goalkeeper has seen out his initial three-month spell with the League One side, but Colchester wanted to keep him until the end of the season.
Colchester lodged an appeal against the Football League after paperwork issues on transfer deadline day meant they could only sign him for a further month.
But the League have refused to budge on their initial ruling - so Walker's time in Essex is now up.
Mark Cousins took over the gloves against Huddersfield on Tuesday night as Walker was ruled out by injury.