I have two "one that got away" stories:
Just this weekend I was at a (crowded!) antiques fair. I had made one loop around the outside booths, and was about to dive into the center section, when I saw an older couple heading out. They were probably in their seventies, and he was about 6'4", and she not much over five feet, but what really made me notice them was that they were moving three times as fast as everybody else, straight to the door. He had something tucked under his arm, and sure enough - it was a green and white Featherweight case. I though about chasing them down and asking to see it; I assume they got a good deal, and if I'd gotten there a bit earlier, it could have been mine! I've been consoling myself by telling myself that they either paid way more for it than I would have, or that it was just the case, not the machine... I don't really believe either of those stories, but it makes me feel a bit better. I did an extra thorough scan after that; I counted 8 machines, but no other Featherweights.
The other one that got away is my mom's Singer 328. I never really liked that machine - the motor was loud and whiny, it didn't stitch as fast as I wanted, the cabinet didn't have any drawers, and all the design disks and attachments were lost in a fire (before I was born). When she told me she was getting rid of it a few years ago, I said that was a good choice, since she had 3 other machines and hardly used it. Now I wish I had it, though; I could treadle it, which would have fixed my motor issue, and it was a good straight stitcher. It was one of the first things she bought for herself when she left home, and the machine I learned to sew on... I wish I had been as sentimental about it then as I am now!