Recovery of deleted data on SSD / USB Flash
Solution 1:
You're looking for Recuva.
http://www.piriform.com/recuva
(Same people as CCleaner and some other neat tools.) Completely free.
The fact that it's an SSD/USB drive shouldn't make much of a difference. If it is an SSD with Trim support, connected to the motherboard SATA port, and you're on Win7, then you may be in a bit of trouble.
Solution 2:
When a file gets deleted, it's reference from the file table of the storage is simply removed. The data itself doesn't get changed unless you run a program that specifically does this kind of "deletion." This means that the data still exists, but is more or less "hidden," so you'll want to use some external program.
I've always found Testdisk/Photorec (They are two different programs, but they are made by the same people and Photorec is just basically a specific portion of Testdisk) to be absolutely amazing for file recovery, and they are both free to use programs.