Sorry to tell you but you made a big mistake way back when you sold your VRTX shares. Patience pays off my friend.
I am not sure if it is wise to short VRTX. Just because a stock has a big one time upside does not mean it is a good short candidate. One needs to look at all factors regrading a company before they short. VRTX has lots of potential products and any of them could produce news similar to the CF drug.