The 2003 Topps Gold set was numbered to 499, so that makes sense. It's not totally unusual that there isn't one pictured on here, as scans are continually being added - /499 is by no means common enough to expect them to all be here.
My first thought was that perhaps the Gold parallel was a partial parallel and skip-numbered, even though that would be a little odd. But Beckett makes no mention of that. I would say it's out there, as no overwhelming evidence points to the contrary (at least what I could find).
Re: the Colston - autographs can always be tricky. Just because they were released on the checklist doesn't mean that the player ended up signing the cards or that they were ever released. Personally, I think that's why so many auto's these days are sticker-graphs rather than on-card - have the athlete sign a ton of stickers and don't worry about what cards they end up getting stuck on. But I digress. Point is on the Colston it's defintely possible (and more possible than the Knight) that it was never produced/released.
I'll never quit collecting entirely, but I am downsizing. Check out my COMC store and help me thin out what I don't want so I can buy cards that I do want. See something you like? Send me a message on here, and we can knock the price down quite a bit. I'll even take a bit of a loss if it means getting you a card you really want.
