I can understand your feeling of being overlooked. It really depends on the convention. Sometimes you'll have judges that know a little about everything or at least one on the judge's panel that knows something besides sewing. And there are cons that have purely sewing experts.
Just last year a group of mine were being judged for our Mass Effect armor. Which is purely fabrication and no sewing involved. However, our judges' experience was limited to sewing (historical sewing only). When explaining the process we all went through and how long it took to make our armor they didn't seem to care and the only question they asked was if we sewed anything. O_o It is a sucky feeling when you know you've worked so hard on such things (for months!) and they get overlooked so easy because of the lack of experience judges may have with materials you have used.
I wouldn't feel upset about it. It must have just been that set of judges. Most cons I've been to will have judges with different fields of expertise. You just have to brush it off and go to the next competition. ^_^