Lightroom photomerge missing images - fix in photoshop?

I'm using Lightroom photomerge a lot but it regularly can't use a few images - generally if it's leaves on a tree etc. Maybe they've moved in the wind. 

im wondering if anyone knows how to take the incomplete image after the merge and drop the missing images in manually in photoshop or similar?

i know how to edit in photoshop but is there a simpler process?