If my child has both genes for celiac disease, but I only have one of them, does that mean the other gene came from the other parent?

The genes for celiac disease are not dominant and recessive. A person can have DQ2, DQ8 or both, and still be at risk for the disease. Genes are either passed from parents to child or not. If a child has both genes and a particular parent only has one, then the other gene must have been passed from the other parent.