This is the second time i've heard it. I've been keeping a close eye on him ever since the first time I heard it a little while back. I read this in the VPI book

"If one of our children sneezes, we do not rush him to the pediatrician. But if he sneezes a few times one day, and more the next and then we happen to notice that there are a lot of snotty tissues in the wastebasket placed there during the night, and the next morning he is congested, breathing through his mouth, coughing, and doesn't feel good---then we take him to the doctor."

The first time he did it was some time ago. It hasn't really been a progression of symptoms. It's been a heavy cough once or twice, and then he's back to normal, or so it seems. I know it could be an underlying problem and "looking normal" isn't good enough.