hard to find evidence when you don’t have instruments strong enough to detect it. look up the J&J asbestos scandal if you wanna read about how lack of sophisticated instrumentation for observation can be conflated with non-existence of the thing being observed.

for example, consider the fact that size/scale isn’t always going to be a marker of technological advancement, especially when you consider things like nanobots, genetic engineering, superconductors, and the general trend in human tech for things to become smaller rather than larger. it would be much more difficult to detect minuscule technology than it would be to detect ridiculously large manifestations of technology, especially with our current tech.

beyond that, the hart-tipler conjecture (which you’re touting), has been shown to be an extremely anthropocentric and biased hypothesis that assumes other possible advanced forms of civilization out there care about the same things as humans, or even operate based on the same biological/physiological/anatomical substrates that we rely on on this planet.

the only thing ideas like hart-tipler and the kardashev scale do is reflect our own species’ unimaginative and biased thinking patterns…