Just because a fax is sent doesn't mean that the receiver read the content. Were there even details about the issue on the fax or was it yet another "call me now in order for me to explain the issue while I could do it by email but I want you to give me money first" type of thing? Can we blame someone to not respond to a fax that doesn't include any details about the issue or how to reproduce it?
The faxed document is linked from the article, no need to speculate what it did and did not include. Hint: as the article says, it includes full reproduction details for the bug.
Just because certified mail is sent and signed for doesn't mean the receiver read the content. The point is that someone got the message, what the recipient does with that message is totally on them.
