The agent is not going to go out of their way to find issues, so they probably didn’t know. The owners are supposed to declare it, though, the agent would have asked about any known things.

If the owners didn’t do rhe change they might not have even known it wasn’t consented. We tend to overestimate people’s knowledge in such things but for most people they only learn about issues when they come up against it for some reason (insurance, selling, etc).