Is that anything like the 'Atkins' diet? :)
I can't think that your low carb diet triggered your UC, especially since you were only on it for 2 weeks when you first noticed UC symptoms. For me, it was generally a low carb (lots of veggies, meat/fish/poultry), antifungal diet (eliminating grains and sugar for a period of time) that helped me get well again; now no symptoms, no meds. I don't advocate the Atkins diet, either. I do think it is too strict. There are better, and easier ways to lose weight, and get healthy again.
Something to consider though, if you can remember that far back, is whether you were on any antibiotics, or birth control pills before your symptoms appeared. Both can be responsible for a fungus/yeast overgrowth.