Well, the way I worded the bit about the box to them went about like this.

"As you detect the room for magic, you sense only your own belongings, the flight-capable wings on the back of the knight handing the box to you, his weapons, all the weapons of the sergeants around you and that's all you sense. For some reason that currently escapes you, however, you are not capable of detecting any trace of magic within the box, as your detection cannot pierce it's adamantium walls."

So I basically told them "You don't know what's in the box"
Which caused a mass amount of curiosity from everyone, and they tried every trick in the book to get it open.