What if upstream answers: ok, thanks for bug report, please try this patch... or I've fixed it in repo, please try svn snapshot, if it's fixed for you?
In that case we can roll a fixed package (e.g. as a scratch build). (If upstream says "try a current snapshot, it should be fixed", I'll usually try to find the actual commit and, if I don't find it, ask "can you please point me to the commit that fixed it so we can backport it?". But for some packages, just upgrading to the newer snapshot is the better solution.) But until that happens, there's no reason for the packager to be involved.
Yes, but how will you notice reporter needs (your) help if bug is closed upstream?