There are many more rocks in our own solar system than there are interstellar spacecraft. Assuming similar proportions elsewhere makes us conclude it’s never aliens.

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.