Dinosaur island content lost after backup/clear/restore

I unlocked Dino Island on my son's iPad Mini using 830 coins.
Dino Island kept on crashing (see 25492) so I did a backup, factory restore, and restore.
When I loaded my game, all my coins were gone and my Dino Island was locked again.

When I unlock Dino Island, where is that transaction kept and why did it not get restored?
Is it a bug that it's not restored?