[jerf]

Beware of metaphors when trying to understand computer issues. What happened (assuming this is the truth) is that a useless key was left on a public server in a public directory, and it could be downloaded by anybody, at which point it is useless. There is no helpful physical analogue to this situation. Just understand it as it is directly, it's not that complicated.

Your metaphor clouds the issue, it does not bring understanding. "Breaking in" to a computer network doesn't give you access to a "whole house", and what occurred wasn't a break in, there's no part of that metaphor that actually helps you understand the situation.

At best this shows a bit of carelessness, but then, a useless, expired key doesn't necessarily require much care in handling, either. The only damage here is PR, if what the company says is true.