No, I wouldn't say a thing. I've had bad check out clerks before. Some of the time, three weeks later they are the best ones in the store. They were just new. Other times, they never turn out to be that great, so I just avoid that line if possible. And If I get in it, I just try to smile, be nice, and help the poor person out as best I can (as I keep an eye on the prices). I can't imagine it was a great day for the clerk either.
But I do feel for you OP. I know when I had morning sickness, I had about 5 minutes in a grocery store before I felt horrible. I can imagine your misery.