A branch cannot be completely deleted after being pushed to a repository created by fork

This started with a disaster. One of my mistakes pushed a code that shouldn’t be published to a repository created by fork. I first discovered and deleted the repository and fork a new repository from the source repository. But after a few hours, my colleague told me that my push operation was discovered and the relevant url was provided. This connection is /username/repository name/tree/commit hash. And I found that the code can be seen by replacing the username in this url with the user who forks the repository.

In fact, this url cannot be reached by any element on any GitHub page, and it cannot be switched to the branch be erro pushed if it is cloned to a local repository. But the web crawler can find the code .
I have sent a help request via contact github but have not received any response. Company also sent the DMCA. But now this code is still able to reach through url

Is there anyone who has encountered a similar situation? How can I solve it? If this is a bug in github, how can I contact the official staff of github more directly?

Things are fixed. Github replied that they cleaned up the cache and the url is no longer accessible