What happens to git commits created in a detached HEAD state?

Your commits are still available in the reflog, as pointed out already. In addition to the other answers, here is a way to take over the detached HEAD commits into your current branch directly, without creating and merging a new branch:

1. Look up the SHA-1 hashes of the commits you made in detached HEAD state with

    git reflog
   

2. Then execute, with all the commit hashes ordered from oldest to most recent:

    git cherry-pick <hash1> <hash2> <hash3> ...
   

   For example if I had only one, given in the "first 7 characters" short hash format:

    git cherry-pick a21d053
   

This will add new commits to your current branch, one commit per detached-HEAD commit that you mention in the command. It also takes over the original commit messages.

The old commit is still in the reflog.

git reflog

This will show a list of commits, and the "lost" commit should be in there. You can make it into a new branch. For example, if the SHA-1 is ba5a739, then you can make a new branch named "new-branch" at the old commit with:

git branch new-branch ba5a739

Note that "lost" commits will get deleted when the database is pruned.