http://www.wrongdiagnosis.com/c/celiac_disease/intro.htm
A link to celiac disease (gluten/wheat intolerance/allergy). Note there are links at the bottom for more information, including one on symptoms. Symptoms include joint pain, weight loss, diarrhea, gas and bloating--something a lot of people on here complain about--and it says that it is frequently misdiagnosed as IBS. Right now 1 in 5,000 people are diagnosed, but that could rise as high as 1 in 250 if testing for it was standard.
So, if you have some of the symptoms listed and haven't been tested, make sure your doctor tests you at your next appointment. Curing your IBS could be as simple as going wheat free (which is nearly impossible to do unless you start cooking everything from scratch, BUT, that's still better than untreatable gas, bloating and diarrhea).