Lost some files in a Git versioned project and could only recover them... in a fork on Github

Lately I realized that I had lost some files in one of my projects hosted on Github, jquery.transition.js. I searched in the commit history to try to find when and how that happened but couldn't find any related commits.

Then I looked at its network graph on Github and found all of the commits and files in someone else's fork: https://github.com/ammonkc/jquery.transition.js/tree/gh-pages

I'm wondering how this is possible. Could it be that I inadvertently deleted the gh-pages branch and overwrote it? Shou开发者_运维技巧ldn't that appear in the commit history?

What usually can happen is:

• a branch deleted or a forced push where those commit are no longer referenced
• a fork done prior to that event which still referenced said commits

Such a push (with a rewritten history without those commits) can only happen if it is "forced" (push --force), but wouldn't leave a trace in the visible history (since the commits have been rewritten).
Even in the worst case scenario, the lost commits are still referenced in the reflog, which you can:

• ask for at the GitHub support (they can create a branch referencing said lost commits).
• or (as repo owner) query the GitHub events API:
  See "Does GitHub remember commit IDs?"