Is it possible that one page got sandboxed?

One of my posts that ranked on the third place on Google is not showing up on the Google search results anymore; It has been for a week. I checked its ranking and it was not even within the top 500. It seems that the post is completely de-indexed by Google. I did build large amounts back links using SB to that specific post a week ago. Could that be the cause? My questions are: Is it normal that a specific post got sandboxed instead of the whole website? What you suggest in order to get that page out of the sandbox? Thanks guys!