I'm the user with this card. I really hadn't thought much of it since I acquired it (I TC Mets primarily and got this on COMC). But I hadn't ever seen it for sale before or after. I did, however, find it a little bit odd that it wasn't listed in the checklist for this set and only suggested adding it when I was logging my collection into the site.
I think this card was not supposed to have been released. If you look at the autograph on the card (or on the sticker), as compared to other John Maine AU cards (I have an '07 Topps highlights AU in my collection as well), it's not the same autograph. I don't know if this means that they stuck the wrong autograph on these cards, or Topps ran out of Maine autograph stickers or whatever. But it appears that this card must have been pulled because the wrong autograph is on it.
It does beg a couple of questions, though:
1) Whose autograph is it, actually?
2) How did I end up with one (and, to be honest, it didn't take me long to find this)?