Do you change your keywords or titles? if you change it, it will deindex it. otherwise you have to wait for some more days.
it happens, at least has happened to one of my sites in the past.I posted a blog post 1 week ago, it indexed, and it ranked for the title page keyword. Now when I check, the indexed blog post is nowhere to be found. Is this a normal occurrence? I'm hoping it will reappear in the serps soon.