You just keep going with the non-sequitur, but now you're also moving the goalpost. Your original statement didn't contain anything about "directly accessible from a public network" (which I assume isn't the case) or "source code known and published" (which you said wasn't the case).
And it is still a non-sequitur. Why would anybody expend non-trivial resources to find exploitable flaw in an open-source codebase to actually bring down emergency service? There's no reasonable way to profit from that. If you're some foreign hacker, you might want to find the exploit, but you wouldn't attack right away. Again, I'm not saying nobody would possibly do it, but one does not automatically follow from the other.
Heartbleed really is the best example on how a critical piece of software infrastructure (including a lot of government regulated infrastructure) had a publicly visible flaw that went undetected (and presumably unexploited) for several years.
> That is how employment works in the wider world of Internet Widgets etc. but not in critical government regulated infrastructure like emergency services.
I don't know man, I'm here arguing with this guy who doesn't seem to grasp a basic concept in logical reasoning, yet he's working on critical government infrastructure.