How'd it go at church? I hope you are feeling better....
You know, it's quite common for IBSers to feel incomplete evacuation. It sucks big time, but it happens. Usually I just try to run to the bathroom the second I feel the cramps come on. The odds of being able to have a BM when you're having cramps is better than when you wait for them to go away.
In this case it might also be good to get one of those sticky heating pads. They are obviously portable and super inconspicuous... you could wear it to church. Weather permitting, of course. It would not be good to have a heating pad stuck to you when you're out in 100 degree weather.
Let us know how you're feeling and if you made it through church OK.