A quick drop of 200+ SERPs for only one keyword on a relatively new site sounds to me like a Google penalty rather than the "dance".
When sites are young it is very easy to overdo the adding of backlinks, or, to succumb to paying for high
PR backlinks, or, to pay an inexpensive foreign
SEO to add a few hundred (spammy) links at "only $1.40 per link!"
All of these can get a single keyword knocked down for awhile in my experience. Examine your recent linkbuilding efforts to be certain you haven't done one of the above. If you have then STOP IT; things will return to normal in a few months after which you can resume building links moderately and correctly.