Could it be that you ate something with cinnamon in it? Some cinnamon (especially when bought in bulk) has an anti-clumping ingredient in it that can contain gluten. It's gotten me before!
Holy crap really? I've never heard of that before, that's pretty scary. That being said though, I didn't eat anything with cinnamon on thanksgiving. It's possible that it may have been a kitchen contamination issue, since my kitchen is not a gluten free one. My mother was the one preparing all of the food. Of coarse she knows I'm a celiac and was trying her best to make me separate food, using separate utencils and taking all the usual precautions you would take to prevent contamination. But a mistake might have been made somewhere along. I'll know better next time and just prepare my own food myself to keep in bins, while staying away from what everyone else eats. I'm sure she'll understand.