I have two stories to tell. The first is in Home Ec in high school. This must have been the third year as I made a blouse and jumper (a low cut dress that needed the blouse underneath). The jumper was brown corduroy and I sewed the full length zipper the entire way through the front as well as the back.
The other big booboo is, a couple of years ago I bought a pattern from a well known big name quilting instructor. I cut a lot of the pieces. Then I tried to make a square. The pieces that form the second or third tier out from the centre are too small. I thought that I must be doing something wrong so I asked for help from the ladies that I quilt with who have decades of experience but it is not operator error, those pieces are too small. So now I have all those cut pieces. It is still sitting there.
I agree about the mystery quilts. I have one I want to make - I first saw it three years after it was run.