Somehow I managed to “Un-weld” an edge of polys before UV mapping the entire mesh.
What’s the best way to go about fixing this? (my guess is retopo the missing polys)
I tried to Import Merge, and also Split, then merge weld + UV.
Attachments
Dynamesh is the only way I know…reproject maybe, I hate it when that happens. 
You can use pinch to pull the verts back together.
export out your mesh
import you mesh and make sure WELD is turned on in your import options.
Tada.