I just went through my moms wallet last week and saw she had her social security card in there...I made her take it out, you are not supposed to be carrying those cards on you...when my daughters came recently it was attached to a card that said to put it in a secure place and not carry it around in your wallet or purse.
Hopefully it was just someone looking for money and they will either stick it in the mail like someone did with my moms or throw it in the trash and someone wont ever find the SS card!