There is no way to get it back without special tools. unlink deletes it immediately. Not to the trash like you would think. Rarely do I see a file or folder delete function that will send it to the trash without some kernel calls. If you were on Windows, you could use Recuva by Piriform.
The reason you can get it back is that when a file is deleted, its file entry is really marked as deleted. Recuva looks at all the file entries and shows you ones that are marked as deleted. I'm not aware of a Mac tool that will help you. But your best bet is to get the hell away from the machine and take it to a computer professional.
ddor whatever other data, you're looking at a hard drive ISO and some expertise. I would give it to a trusted specialist and not do it yourself if you really want to save it with the greatest chance of doing so. – Jared Farrish Jun 23 '12 at 19:24