I joked about using Search the Web to find it by typing in "freaky accidents."
But I totally did find it. Going off of solely my memory of a fic I DID NOT EVEN READ 12 years ago, and my ability to recognize its title and find the scene I'd skimmed TWELVE YEARS AGO, which wasn't even in the first chapter.
I'm being vague because I don't want to say anything bad about someone's fic if it's identifiable, even though it was written 12 years ago and the person has not even been in SPN fandom for I'd guess about as long.
BUT OH GOD THIS IS MY ONE SUPERPOWER IN LIFE. THIS AND ONLY THIS.
I CANNOT. BELIEVE. I FOUND IT.