aakk9999 - 7:39 pm on Jul 12, 2013 (gmt 0) [edited by: aakk9999 at 7:40 pm (utc) on Jul 12, 2013]
Just to exclude the obvious:
Have you checked your robots.txt? Just in case it is not disallowing the site?
It would also be good idea to try to do "Fetch as Googlebot" few of URLs that have lost the traffic to make sure Google can fetch them.
[edited by: aakk9999 at 7:40 pm (utc) on Jul 12, 2013]