Prompting Meme Question

Let me set the scene: quite a while ago now, I read a prompt on a prompting meme that I thought was genius, but didn't have any idea for, so I just moved on and basically forgot about it.  Fast forward several months, and I wrote a fic inspired by that prompt but a) it's pretty sideways from the prompt, in that it includes the sequence requested, but doesn't focus on it at all and b) it's a crossover with another fandom, and not just incidentally, characters from that other fandom are very central to the story.

Now, I have no problem citing the prompt- I have every intention of saying "Hey, guys, check out this prompt, it totally gave me this idea" and linking to it- however, I don't quite feel right calling it a fill and posting it on the meme (no, I haven't checked if someone else has filled it already, but I will soon, and if someone has it will ease my mind considerably), but I do know that some people do and just say, "Sorry, sideways from the prompt."

My question is: does anyone know if there is a generally accepted etiquette for prompt fics that sort of went haywire?