You did not catch that Bluej.
Say the planet is 1000 light years away, for the sake of discussion.
1,000 years ago, the signal we are hearing today was sent. So if WE respond, it will be another 1,000 years before they hear it. 2,000 years would have lapsed from the first transmission to the acknowledement of the message.
2,000 years will also pass here, before we know if they heard our response.
Who is going to be here in 2,000 years?