I accidentally deleted everything from Sony Xperia P
Simply, follow the steps from the link you posted, if you already tried that but still same, you can always flash the stock ftf file for your phone using flashtool, and then you can install cm12 again if you want with the same steps, 


  Sony Xperia P LT22i FTF: Download #4.1.2
  
  Flashtool: Download     #latest version
  
  Guide for using FT: HERE