You need to contact your caseworker. In most states, you get some kind of letter saying your food stamp benefits have been cancelled & laying out the reason(s) why. We can offer nothing to help except to suggest you make that call, send her a certified letter to make sure she receives it, or call HER supervisor!
I don't think you did anything wrong for you not to receive your food stamps. There might have been some confusion somewhere for you not to have received your food stamps for the said date. The best thing to do is to contact them and ask what went wrong.