It is possible to retrieve data and pictures from a "wiped" memory card because all what happens when you "wipe" or erase the card is that it allows the camera to overwrite the info already on the card.
I had a embarrasing cock up recently when I lent my digi cam to a neighbour telling them not to bother to take their old fashioned film camera as "modern technology - its the way forward" however when they got back from their holidays in Venice the card in the camera had become corrrupted and I thought that they had lost all their pictures.
I managed to download some recovery software and after a lot of messing about managed to retrieve about 90% of the pics.
I think that it is more difficult to do if the card has been Formatted rather than just Erased.
I never did tell my neighbours about just how close they where to having no momentos of Venice!!
If you want to send me the card I'll have a go - no promises though.