Is personal information, such as your credit card number, stored on the key card that you use to open hotel rooms? If so, can that information be stolen if you toss the card into the trash after you check-out?
Hotel key cards only store the room number, and the combination for the room. Personal information is not stored on them, since there is no way to put it on the card, and it would be illegal in the U.S. and probably other countries, as well as a violation of the merchant agreement that all credit card merchants are required to sign and abide by.
If cards are lost, stolen, or thrown away, the hotel can create a new one immediately, with a different combination for that room, so the other key card will not work anymore.
I cannot give you a definite answer, but I very much doubt that such information is stored on a hotel key card. I would be surprised if it even stored the name of the hostel guest.
I suppose that it only stores which room it is supposed to open and for which period.