Can you tell me what materials were given last year?
Sorry, No, that’s why it is called Mystery Architecture. The event description says:
The materials might include pins, cups, straws, paper clips, etc. THIS LIST IS ONLY AN EXAMPLEOF THE MATERIALS WHICH MAY BE USED.
Usually, it is a combination of everyday, easily obtained household/school materials. Sometimes pieces of other stuff, like those from The Scrap Box are mixed in.