I'm sorry that there was miscommunication between you and your therapist. I think you should ask her to explain what she meant.

I would think that a box filled with objects that are significant to you would be better than objects your T places in the box.

Objects the T places would just serve as a way to remember the T. The ultimate goal in therapy is to help you get to a better place. To the point your T can feel like their job is completed.