That day when I was migrating SharePoint site from 2007 to 2013. The site was using FAB40Site templates.
After installing FAB 40 version for SP 2010/2013 from here, I got an issue after visual upgrade as described below.
Error: Unfortunately we found some problems. Missing Site Templates.
After so much searching no resolution was found on internet.
As the issue didn’t came for SP2010 visual upgrade, It means the templates were present for version 2010. Hence, I went to 14 hive Templates folder and copied the missing templates folder (LL, PROJSING in this case) to 15 hive Templates folder.
Again run the Visual Upgrade and mission was accomplished.