Any "unerase" program should do the trick - as long as nothing has been overwritten.
As far as your computer is concerned, your memory card (whether attached via a memory card reader or the camera via USB or however) is just a "removable drive", like a big floppy disk, and any tools to fix those should work on memory cards.
I'd be wondering, though, what was really meant by "erased all the pictures" - surely they didn't go in intentionally and delete them all one by one?
If they accidentally reformatted the card, then a good recovery tool could still get the pics back, but a simple unerase program might not be able to.