I didn't say they'd be looking for us. What I'm saying is that if an alien species were looking for a planet to colonize, they'd be looking for one with similar characteristics to theirs, in order to live in a habitable place, and since we haven't found anything similar to Earth, we'd be just as far and hard to find for them as they are for us.
Sure, it's possible they'd been looking for thousands or even millions of years, but as I've stated before, the likelihood of intelligent life evolving and surviving that long ago, and continuing to survive, thrive, have interest in space travel, then being capable of space travel, then looking for an Earth like planet, and finding us is.....pretty low. Not impossible, but very unlikely.