Yep you can retrieve data by yourself. There are programs to do that. For example Software for Recovering Deleted Files
I used it few times.
But there is a sad news. I'm not sure but most of these programs work with NTFS and FAT32 files systems. I recently tried to find something that would work with ext4 but I was unsuccessful. So, because OS X is using HFS+ file system there could be problem with software. But I can't believe that they don't exist.
To sum up try to google "recovering HFS+ partition" or find program for recovering data that can work with HFS+ file system.