FimFiction Link - Short ID: 163282/rainbow-dash-re-animator
Published: Aug '14 — Oct '14
Also, boy am I glad I went to reread this. I only vaguely remembered it being very awesome and the basic plot summary I posted above, which prompted me to seek it out, and it was definitely a very awesome read.
I was going to add "It's decently popular so I assume most have already read or seen it" but then I went to check and actually it's way less popular than I expected at just 316 likes and not even 4k views. I'd have pegged it as a 1.5k-2k like story. So if you haven't read it yet, consider this a recommendation.