Ugh, I just hate it when doctors do that. Obviously it isn't all clear when your in pain! Geez! Just like my upper GI I had, after I drank all the barium the radiologist said it was a useless test for me because of the way my intestines folded up around my TI. I get a call from my GI a week later telling me it all looked great! When I knew they couldn't see the most important part!
I agree that it may not have just been able to show up on the MRI yet. Is your GP good with these things? Mine is wonderful and that would be my next stop. It took a year for me to find someone who could diagnosis my fistula, it was before I had my current GP. Amazingly it was an urgent care doctor that finally nailed it. I wouldn't just let it go, get another opinion.
Diagnosed with Crohn's Disease 2/06, and Health Anxiety/OCD 12/08 Taking Asacol, Questran, Toprol XL, and Celexa.