I ran into a problem during my upgrade from NIS 2011 - 2012. My identity safe disappeared. I used chat and allowed access to my computer and the tech was able to quickly resolve my problem. The old identity safe was left on my computer under (I have W7) .
C:\ProgramData\Norton\{0C55C096-0F1D-4F28-AAA2-85EF591126E7}\NIS_19.1.0.28\IdentitySafeDataStore\S-1-5-21-2061223589-626851344-1726936180-1001
I'm not exactly sure how the tech was able to drill down using the guid folders(the long alpha/numeric folder names) but I'm glad it was there. This post might explain how to decipher the folder path.
For me, I'll do an export of identity safe myself just before the update. I do a backup of my system every night so I don't need to use NIS to backup it's files. Then if NIS upgrade fails to restore my files, it's easy for me to fix.