I would say an AU where Sam finds him first, but @neonthewrite did one like that, and Sam definitely grabbed first, checked later.

That poor smol might be fated to always be nabbed by the bros.

(Neon – It’s kind of become a running gag that Oscar gets grabbed by Dean in every story from Food and Monsters, as well. I always work it in that somehow, Dean will yoink the little guy.)