peat said:
technology breaks physical limits though.
Perhaps, but you're comparing theoretical technology that might never exist with the Drake Equation.
Even if the sort of terrestrial scanning technology existed that would allow alien lifeforms to scan solar systems on a galatic scale existed, we would need to be MILES more advanced to be of interest to the creator of such a device and actually worth investigating compared to the other lifeforms they would uncover - many of which would almost certainly be more advanced thus of more interest.
For every piece of theoretical technology you can conceive, I'm sure others could conceive a reason for it not to result in aliens coming to Earth.