This has pushed my mind into a philosophical thought pattern. Is the advancement of technology predictably the same for all intelligent civilisations? If we had two tribes on either side of the planet 100 thousand years ago, would they have both have developed clubs, sharp flint, fire, language etc in roughly the same order? Would the discovery of fire predictably lead to cooked food in both tribes? On a larger scale, if we had a second Earth like planet somewhere in the universe would they be making (or have made) the same general discoveries? Once you get stuck into a loop of ever increasing technological discovery can you ever escape and does it always lead to a predictable end?
Perhaps the predictable end is the answer to the question "Where are they?" with one of several answers.
1) They are gone/dead.
2) They are not interested in such an infant civilisation.
3) They don't know we are here.