There's some items here on gaia that, for one reason or another, don't even seem to exist unless it's in the MP. I've been searching around for ages to find out where a couple of my quest items are from with no avail, it's like they just appeared.
That being said, I feel like there should be some decent re-release type items that bring back some of the more sought out items.
If you look at your wishlist and click on the item, you can at least find out the date it was released, then check announcements from around that time.
Or, ask smile Many people might know!
I love re-release bundles, I hope we get a few for xmas!