Heuristcs that almost always work are right up until they're not.

https://www.astralcodexten.com/p/heuristics-that-almost-alwa...

That’s why they’re called heuristics and not deterministics

I mean, sure, but no one I've invited in my home is a vampire so far and I think that heuristic is solid.

You wouldn’t know unless they told you. They could have had a snack someplace else.