You could try sending an e-mail to operations@kumoricon.org, and see if they can help!
If that particular branch of Kumoricon can't help, they might be able to direct you to someone who works in the Lost & Found.
You need to tell them exactly what kind of DS it is (you said silver, but are there any stickers or scratches on it?), and ALL the games that you have also lost - besides Devil Survivor, just in case.
If you're unable to get the DS back before you go home to Ohio, you should give staff your mailing address so they can send the stuff to you.