[bhaak]

Then we have almost no chance to detect it anyway unless we almost spot on between sender and receiver. But this is a similar constraint to detecting exoplanets with the transit method. Star, planet and Earth have to be in one line for this method to work.

We are detecting lots of potential planets with this method, so if technical alien civilizations were as abundant as planet we should have detected a few already. ;-)

BTW, we ourselves stopped to do the "blasting a signal in every direction" like we used to 50 years ago. With fiber optics, satellites, and other modern technology, we are leaking much less electromagnetic radiation. The chance of another civilization picking up us is shrinking.