Recovering lost partition is a complicated process. You better take help of professional crash recovery service. Bear in mind that it is gonna cost you money.

I read it somewhere that gpart command used by forensic experts to recover data or evidence.

From gpart site, Gpart is a tool which tries to guess the primary partition table of a PC-type hard disk in case the primary partition table in sector 0 is damaged, incorrect or deleted. The guessed table can be written to a file or device. Supported (guessable) filesystem or partition types. Since I never used this tool I cannot comment out. Read the site and see if it can help you out.

http://www.stud.uni-hannover.de/user/76201/gpart/

Good luck with parition recovery