I just got done with a friendly PM exchange with Heavy G.
His story has no mention of Type O- blood.
So that question is now resolved in my mind. And it also makes me feel more free to "borrow" that plot element for myself.
I honestly do not recall where I read about that one in the past. But it was a message forum discussion somewhere (I thought it was here) where someone mentioned a future dystopia where people with Type O- blood were deemed valuable enough to capture and hold prisoner for their blood. I have been tempted to incorporate it into my story, but hesitated for a long time. Now I think I will be a little bolder about it.
And as one parting comment about plagiarism: a lot of writers don't always recall where the heck they pick up these tidbits and idea, but such brilliant little nuggets and story fodder offerings can be sneaky little buggers, seeping into a writer's imagination and taking hold. And then the hesitation comes from the dread fear of asking: "Has this been done before?"