I think a civilization like ours might be hard to miss, but if they only hit e.g. stone age levels we could easily miss that. Of course it depends on the time

I think a civilization like ours might be hard to miss, but if they only hit e.g. stone age levels we could easily miss that. Of course it depends on the time scale. An industrial civilization 250mya might leave little traces unless you knew exactly where to look and what to look for. There is also the hidden assumption that they would build the same sorts of things as us for the same reasons, a form of anthropocentrism.