Strange things happen in stock market (and off-market)

I am holding shares of a company 'Divyashakti Granites' for more than two years now. I had bought them at an average price of around INR 25 when the book value of the company was very high and even the net current assets are higher than the price. What I found was that in the month of June, there was an off-market transaction where somebody bought shares of the same company off-market for just INR 12. I have never seen something like this happening in any of my holdings earlier. The price of the scrip has moved from INR 25 to 31 now. This really is strange!!!!