hey i found a memory card of a camera of someone else. while travelling in australia. on the camera were also videos where you could hear them talking in german. they also said names...
anyway, i went on facebook joined a group called "german travellers in oz" or similar and posted two pictures of some guys that were on many pictures as probably one of them is the owner or at least a good friend of him.
after a short time someone recognised the owner and i sent him his card. He was really happy, pictures he thought were lost came back.
i found another memory card, similar story. but sadly noone replied on that...
you've got the town close to his home. the chance that someone in philly knows him is verry high. and the chance that this person is the same age is even higher. so if he is at highscool try to ask in a facebook group of the highscools in philly and maybe some other in towns around. just make sure you dont give any information that is not needed. and preferably edit the picture you have and crop it, so you can only see his face.
cheers and good luck