There could be a genuine necessity to get your site or page crawled by Google right away instead of waiting for Google to come and crawl your site. Imagine a situation like this. You created a lot of valuable content and added to your site that you want to be indexed and available for search or say you created a valuable link which is valuable from SEO purpose and unless the site/page is crawled and indexed, there is no SEO value that is coming to come your way. So, at times, it may be natural situation where you might like to request Google crawl a site or page of your own or even a page or website that you do not own!
How, please refer to https://support.google.com/webmasters/answer/1352276
To ask Google to crawl a URL on a site that you don’t own, use the URL https://www.google.com/webmasters/tools/submit-url/.
If the site belongs to you and registered in webmasters tool, go there and do as follows:
Ask Google to crawl a page or site:
1. Click the site you want.
2. Under Crawl, click Fetch as Google.
3. In the text box, put the URL you want to check.
From the drop down list, select Web and then click Fetch.
Once you get a status of “Successful”, click Submit to Index, after choosing one of them:
1. To submit single URL to Google’s index, select URL and press Submit. Maximum up to 500 URLs you can submit this way in a week.
2. You can also submit the URL and pages linked from it but up to 10 such requests are allowed a month.
Hope this helps. For details refer to here.
ref – http://www.searchenginejournal.com/how-to-recover-from-getting-de-indexed/51529/#comments