(a) to the best of everyone’s knowledge it is impossible to hide your heat signature in space, let alone hide the shadow of a planet blocking the light of its star (metamaterial cloaks are far too frequency-specific)
(b) the biosignatures we’re looking for right now are anything out of chemical equilibrium, so a planet-dwelling civilisation would only hide from us if they wiped out their surface and ocean ecosystems at the very least
(a) to the best of everyone’s knowledge it is impossible to hide your heat signature in space, let alone hide the shadow of a planet blocking the light of its star (metamaterial cloaks are far too frequency-specific)
(b) the biosignatures we’re looking for right now are anything out of chemical equilibrium, so a planet-dwelling civilisation would only hide from us if they wiped out their surface and ocean ecosystems at the very least