That reminds me of the story about the guys who discovered that many gastric ulcers are (ultimately) caused not by stress, or by peppery food, or anything like that, but by a bacterium. They were working on some drug for treating ulcers and did a controlled study to see if it worked. The experimental group was given their experimental drug. The control group was given daily doses of Pepto-Bismol as a placebo.
The drug was a failure. People using it got better, but not at a higher rate than the people in the control group.
But wait. The subjects were getting better. The drug worked. It just didn't work better than daily doses of Pepto-Bismol.
Yup, it turns out that you can sometimes cure gastric ulcers by giving the patient daily doses of Pepto-Bismol for three weeks. It's an antibacterial agent.