When people empty their recycle bin they kind of understand what is going to happen. Discarding changes speaks to me but evidently not to this person. Personally I tend to put my code in Dropbox in early stages as git commits do not make much sense (of course one can squash everything and do a rebase but that is advanced git already).
Well not that hard, because of course I tried it first on a copy of the project so haven't lost anything (if not time).
But even if I agree that what is going to happen is unclear for some (included me at the time), and a total wipe of your work is excruciating, you don't "try things" on the only copy of 3 months of work.
Anyone who has anything important on a computer should know to back it up somewhere.
Even most of my relatively computer-illiterate friends and family members do rudimentary backup for their stuff (usually in the form of emailing themselves or just creating a copy).
A three month project without backup or version control shows a lack of basic training.
I wish schools and universities would teach version control on day one of CS courses.
At some point you have to take responsibility for knowing your tools. This is a professional.
He might know how to write code, but obliviousness towards source control (and backups, for that matter) is a HUGE indicator of him not being a professional.
The victim did it to themselves, it's like playing with a loaded gun then complaining when you accidentally shoot yourself in the face. A bad workman always blames their tools. At the very least they should have learnt Git.