The blog author found a bug and submitted a patch, the kernel maintainer fixed the bug differently with his own patch. No copyright was infringed. Where is the theft?
Open Source maintainers don't owe you to accept your patches.
However arguably root cause analysis is a significant part of fixing a bug, often much more work than writing the lines that fix the bug. A "reported by" is not an acknowledgement of this kind of work.
IMO the author earned an opportunity to write the patch themselves with the guidance of the maintainers. What the author got robbed of is this opportunity.
Doesn't work that way when it's declared a security problem. Fix ASAP is the only way forward for those.
I often spend hours investigating bugs I am just reporting. This is because I want to make it reproducible for the maintainer. Sometimes making it reproducible narrow down the issue so much that it can be found in the code in a few minutes. "Reported-By" is often not a small feat.
But the author went further and identified the incorrect parts of the code as well and produced a patch that resolved the issue.
I would sure love if most the bug reports I receive would be of this quality, it would save me a lot of work...
Copyright infringement is not theft