Fabulous Diamond? Where did I find this thing?

So I was going through my pages of hoarded stuff (the pack-rat that I am), and I found a Fabulous Diamond.
I can’t for the life of me recall getting it, and if I’d spent fate on it I’d think it’d be memorable.
Can anyone help me out by giving ways I (may) have come to possess one?

I haven’t got a Fabulous Diamond but I thought the only way to get one was from a Fate-locked way to deal with your nightmares.

2 ways that I know of. Both are fate-locked. The first involves selling your soul, the second involves dealing with your nightmares

Aha, I took the first option a few weeks ago, but clearly did not read the result thoroughly enough. Thanks for the answer!