Because you never git pushed to the fork it's not aware of your repo, you're ok. What I don't know is if in 3 months you DO set your remote origin to that fork

Because you never git pushed to the fork it's not aware of your repo, you're ok. What I don't know is if in 3 months you DO set your remote origin to that fork to for instance, pull upstream patches into your private repo, you're still not pushing, only pulling, so I would THINK they'd still never get your changes, but I don't know if git does some sort of log sync when you do a pull as well. Maybe that would wind up having the commit hash available.