I know which show to which you are referring and I've recently had this same discussion with a few of my fellow guild members. I was asked about the quilt because they knew that I had judge shows and the past and they wondered how something like this could happen. Here is what I told them, but please let me reiterate that I'm only speaking in "possible explanation" terms, since I did not judge this show.
1. Perhaps the quilt was entered into the wrong category. I had to disqualify a BEAUTIFUL quilt that had been entered into the "Mixed" category (patchwork and applique). The quilter had machine pieced and hand-quilted the project. She thought that's what "Mixed" meant. (The category description clearly stated the definition of "Mixed.") She should have entered it into the "Hand-Quilted" category, or the "Machine Pieced" category, and later admitted that she hadn't carefully read the category descriptions.
2. Perhaps the application was not complete, therefore not eligible for judging. (Be sure to fill out all the information and sign the entry!)
3. Perhaps it was a "Display Only" quilt and not meant to be judged.
4. Perhaps there was an issue about "legality." I judged a show once in which an individual listed the quilt as an original design, but it was actually made in a class taught by a somewhat local designer/quilter. Had I not taken the same class and seen this quilt before, no one would probably have known. When the individual who entered the quilt was questioned, she stated that she had forgotten that she had made this in a class. (I seriously doubt that was the case because I heard her say to her husband as they walked away: "I should have known better than to enter it in a show so close to home.")
Anyway, to make a long post even longer. You just never know the whole story. There is the "judges bias" in some cases, but certainly not all. Many shows also have the judges make comments for the quilters. It would be interesting to see if that was the case here.