[420basteit]

I think you have a slight misunderstanding about the great filter.

If we found only microorganisms on the other plant that should indicate that the filter is behind us, life having died out on that planet before even reaching large scale organisms let alone technology.

If we find ruins of civilization and technology on the planet at either about the same stage as us or more advanced, then we can assume that the filter is ahead of us.

[asdfpoiu10]

Not so. All we know from finding micro organisms (or any other form) is that the filter is after that stage. It may well be between micro organisms and us but that seems unlikely.