So you go to all the effort of finding the bug, and documenting the correct fix etc. ... but don't bother to spend 5 minutes opening a distro. bug saying "X is the wrong fix, this is the upstream fix".
It seems to me that the correct workflow would be for downstream packagers / maintainers to discipline themselves to check for upstream changes on a regular basis, rather than relying on upstream to figure out who is packaging their product and notify.
It is incumbent on the upstream developer to have channels available to get the word out -- a developer's list, a bug tracking system, release notes, etc. But it is not reasonable to expect upstream to check the bug trackers of all of the scores of active distributors out there.