I looked for strings that I am sure only appear in my code, and I found several copies of them, but not mine.
Details like this would help the OP to track down the exact cause of why it has indexed the forks but not the original repo.
In my case, I am not talking about forks but about people who copied my files into their repositories (with proper attribution and respecting the license). I just searched for my surname and was happily surprised to see it in major projects like ffmpeg, pytorch, bytedeco, scikit and opencv.