I'm sorry if this has been asked before. I coulnd't find anything with the search function.
I recently used Googe Sitemaps to add a new folder (several thousand pages) to our website. Within a few days, I found the folder's index page listed in Google and showing up in search results. A few days later, I found that the index is no longer listed in Google at all.
Is this a common indexing process? Or has my site been penalized?