I think something was Going on about this since the starting of august, As after the Google Update for August webmasters continue reporting about major loss in there rankings … and everyone was confused about this situation.
Patrick in his post described something similar and this is something everyone noticing including me, Looks like Anchor-Text are no more The Most Important Factor for Organic Rankings.
According to the expirement I performed 2-3 months back, I was able to get ranking for the targeted keyword and I was at Top-10 for atleast 2-3 months and now last night when I checked it was no-where … Strange hun ?
rishil and many more webmasters reported the same thing !! If you have something to say about this issue then feel free to comment 
I have also faced simlilar problem with the websites where I worked . One of my site PR has been down ! I am still trying to undersatnd what to do ?