Oof, and you've got no backups? I'm really sorry to hear that, I wish there was something I could do.
I'd highly recommend getting a Github account and setting up version control for your projects.
It's fine, don't worry. I usually have backups but have been so neck-deep into work lately I didn't remember doing one before installing the new version (I'm a simple guy; I see GB Studio updates, I download and install). I'm not concerned in regards to project files, since most of what I had were placeholders to test movement routines and collisions. The issue is really the references since they were largely my own (bitmap mockups, etc) and while I can resume this at any time, it'll be double work for that. Oh well.
In any case, not trying to be a downer. GB Studio is amazing, please keep up the great work.