Why the article noindex by google?

Recently, I post one article on a high traffic and authority site. First day, it has been indexed by google and get links from other sites. However, I find it is noindexed by google 10 days later and do not find any noindex table in that page. Anyone could help me analyze why this happened and give advice.

need more information to answer

what kind of article, is it unique or not, what size, is it written by hand or is it a spun?