No one's here's ever said that for as long as I've been coming here, and I know that astronomers have long suspected that planets were a routine by-product of star formation and were probably very common.

In fact, long before we found the first one, people were looking very hard trying to find ways to do so. When I was an astronomy student 40 years ago one of the graduate students' theses was about a device he was developing to detect wobbles in star positions caused by extrasolar planets. Van de Kamp, a leading astrometrist, suggested Barnard's Star as having planets as far back as the late 30s. It turned out he was mistaken about this particular star, but his report was taken seriously and cited frequently in the literature.

I think your memory is of the "scientists have proven bumblebees can't fly" variety. That old chestnut never happened either. It's a way of demonstrating how stupid scientists are which can then be used to show that something else they are skeptical about must be true. (Somewhat like UFOs today.)