Ello!
It's been a while, but that's because I've left games to do some VFX work at Double Negative in London!
However, back to Unity problems...
The Problem:
Animation/Geometry not appearing upon import .fbx in Unity. Specifically geometries that had been animated in their scale.
The Fix:
Do not animate to complete 0. Animate to 0.001.
Don't ask me why, Unity is a mysterious woman, yadda yadda yadda.