Well, unless they can see the future, they couldn't have known you were going to delete it before you did :P. If there is some delay baked in, and it cares about whether the chapter is still there, all it takes is a little experimentation (or data-gathering on how long it takes to get an alert from when the chapter is posted) to find the length of time you need to leave it up for. That said, I am unfortunately not signed up for the alerts, so I can't confirm for you whether it worked.