the person who posted the ad joined just to post it. Only posted once, has not been back in the forum since it was posted.
If you are ever in doubt just click on their user name and you can see what type of activity they have done and when was the last time they visited the forum.
Of course you can also try sending them a private message. Because unless this individual took the time to subscribe to this thread and receive notifications there was activity on it they are never going to see that you have asked them if it is still for sale
If you are going to respond to a thread that is not current do take the time to see if the person you want to have a conversation with is still around and active.