Each new post is scheduled to be stored into a search index, at regular periods of time. Therefore, if you created a new post, it will take approximately 10 minutes before your post content will be recorded and displayed into search results.
For example, while viewing the Advanced Search
or Search Results pages, you will notice at the top of the page a message like:
"The search index was updated 8 minutes ago."
That means the next index update will be executed in approximately 2 minutes.
The forum administration might change at what interval of time the index updates can occur.