For the computer to 'see' the drive again you will have to finish reformating the drive. There should be some sort of disk utility to help you with this? You can also use command prompt (terminal) to fix this issue as it can see behind the operating system and see the drive (google reformatting hard drive in command prompt). There is also free software available that may do this also.
I'm not sure if you can save the data you could try 'Pandora recovery' . Don't do anything if you want to keep the data...