I did a mistake when working on submodule clone instead of a manual cloned repository.
That means as I checked out the master branch, my commits from the previous ‘no-branch’ state where reverted. To save them just do it like that:
cd cloned-repo
git reflog
git checkout master
git cherry-pick sha_of_the_missing_commit
Note to myself: Always check out the master branch before modifying submodule clones.